AD ADA4817-2ACP-EBZ Low noise, 1 ghz fastfet op amp Datasheet

Low Noise, 1 GHz
FastFET Op Amps
ADA4817-1/ADA4817-2
Data Sheet
CONNECTION DIAGRAMS
ADA4817-1
TOP VIEW
(Not to Scale)
PD 1
8 +VS
FB 2
7 OUT
–IN 3
6 NC
+IN 4
5 –VS
07756-001
High speed
−3 dB bandwidth (G = 1, RL = 100 Ω): 1050 MHz
Slew rate: 870 V/µs
0.1% settling time: 9 ns
Low input bias current: 2 pA
Low input capacitance
Common-mode capacitance: 1.3 pF
Differential-mode capacitance: 0.1 pF
Low noise
4 nV/√Hz @ 100 kHz
2.5 fA/√Hz @ 100 kHz
Low distortion
−90 dBc @ 10 MHz (G = 1, RL = 1 kΩ)
Offset voltage: 2 mV maximum
High output current: 40 mA
Supply current per amplifier: 19 mA
Power-down supply current per amplifier: 1.5 mA
NC = NO CONNECT
Figure 1. 8-Lead LFCSP (CP-8-2)
ADA4817-1
TOP VIEW
(Not to Scale)
FB 1
8
PD
–IN 2
7
+VS
+IN 3
6
OUT
–VS 4
5
NC
NC = NO CONNECT
07756-002
FEATURES
Figure 2. 8-Lead SOIC (RD-8-1)
APPLICATIONS
ADA4817-2
14 +VS1
13 OUT1
16 FB1
15 PD1
TOP VIEW
(Not to Scale)
+IN1 2
12 –VS1
11 NC
NC 3
10 +IN2
–VS2 4
9 –IN2
FB2 8
PD2 7
OUT2 5
+VS2 6
–IN1 1
NC = NO CONNECT
07756-003
Photodiode amplifiers
Data acquisition front ends
Instrumentation
Filters
ADC drivers
CCD output buffers
Figure 3. 16-Lead LFCSP (CP-16-20)
GENERAL DESCRIPTION
The ADA4817-1 (single) and ADA4817-2 (dual) FastFET™
amplifiers are unity-gain stable, ultrahigh speed voltage
feedback amplifiers with FET inputs. These amplifiers were
developed with the Analog Devices, Inc., proprietary eXtra Fast
Complementary Bipolar (XFCB) process, which allows the
amplifiers to achieve ultralow noise (4 nV/√Hz; 2.5 fA/√Hz)
as well as very high input impedances.
With 1.3 pF of input capacitance, low noise (4 nV/√Hz), low
offset voltage (2 mV maximum), and 1050 MHz −3 dB bandwidth, the ADA4817-1/ADA4871-2 are ideal for data acquisition
front ends as well as wideband transimpedance applications,
such as photodiode preamps.
Rev. B
With a wide supply voltage range from 5 V to 10 V and the
ability to operate on either single or dual supplies, the
ADA4817-1/ ADA4817-2 are designed to work in a variety of
applications including active filtering and ADC driving.
The ADA4817-1 is available in a 3 mm × 3 mm, 8-lead LFCSP and
8-lead SOIC, and the ADA4817-2 is available in a 4 mm × 4 mm,
16-lead LFCSP. These packages feature a low distortion pinout
that improves second harmonic distortion and simplifies circuit
board layout. They also feature an exposed paddle that provides a
low thermal resistance path to the printed circuit board (PCB).
This enables more efficient heat transfer and increases reliability.
These products are rated to work over the extended industrial
temperature range (−40°C to +105°C).
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ADA4817-1/ADA4817-2
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Driving Capacitive Loads .......................................................... 15
Applications ....................................................................................... 1
Thermal Considerations............................................................ 15
Connection Diagrams ...................................................................... 1
Power-Down Operation ............................................................ 15
General Description ......................................................................... 1
Capacitive Feedback................................................................... 16
Revision History ............................................................................... 2
Higher Frequency Attenuation ................................................. 16
Specifications..................................................................................... 3
Layout, Grounding, and Bypassing Considerations .................. 17
±5 V Operation ............................................................................. 3
Signal Routing............................................................................. 17
5 V Operation ............................................................................... 4
Power Supply Bypassing ............................................................ 17
Absolute Maximum Ratings ............................................................ 5
Grounding ................................................................................... 17
Thermal Resistance ...................................................................... 5
Exposed Paddle........................................................................... 17
Maximum Safe Power Dissipation ............................................. 5
Leakage Currents ........................................................................ 18
ESD Caution .................................................................................. 5
Input Capacitance ...................................................................... 18
Pin Configurations and Function Descriptions ........................... 6
Input-to-Input/Output Coupling ............................................. 18
Typical Performance Characteristics ............................................. 8
Applications Information .............................................................. 19
Test Circuits ..................................................................................... 13
Low Distortion Pinout ............................................................... 19
Theory of Operation ...................................................................... 14
Wideband Photodiode Preamp ................................................ 19
Closed-Loop Frequency Response ........................................... 14
High Speed JFET Input Instrumentation Amplifier.............. 21
Noninverting Closed-Loop Frequency Response .................. 14
Active Low-Pass Filter (LPF) .................................................... 22
Inverting Closed-Loop Frequency Response ............................. 14
Outline Dimensions ....................................................................... 24
Wideband Operation ................................................................. 15
Ordering Guide .......................................................................... 25
REVISION HISTORY
5/13—Rev. A to Rev. B
Changes to Figure 3 .......................................................................... 1
Changes to Figure 7 .......................................................................... 7
Updated Outline Dimensions ....................................................... 24
Changes to Ordering Guide .......................................................... 25
3/09—Rev. 0 to Rev. A
Added 8-Lead SOIC Package ............................................ Universal
Changes to Features Section and General Description Section . 1
Changes to Table 1 ............................................................................ 3
Changes to Table 2 ............................................................................ 4
Changes to Figure 4 .......................................................................... 5
Changes to Figure 9, Figure 11, and Figure 12 ............................. 8
Changes to Figure 21, Figure 22, and Figure 24 ......................... 10
Changes to Figure 33 ...................................................................... 12
Added Figure 34; Renumbered Sequentially .............................. 12
Changes to Thermal Considerations Section and Power-Down
Operation Section ........................................................................... 15
Changes to Capacitive Feedback Section and Figure 46 ........... 16
Added Higher Frequency Attenuation Section, Figure 47,
Figure 48, and Figure 49; Renumbered Sequentially ................. 16
Updated Outline Dimensions ....................................................... 24
Changes to Ordering Guide .......................................................... 25
11/08—Revision 0: Initial Version
Rev. B | Page 2 of 28
Data Sheet
ADA4817-1/ADA4817-2
SPECIFICATIONS
±5 V OPERATION
TA = 25°C, +VS = 5 V, −VS = −5 V, G = 1, RF = 348 Ω for G > 1, RL = 100 Ω to ground, unless otherwise noted.
Table 1.
Parameter
DYNAMIC PERFORMANCE
−3 dB Bandwidth
Gain Bandwidth Product
Full Power Bandwidth
0.1 dB Flatness
Slew Rate
Settling Time to 0.1%
NOISE/HARMONIC PERFORMANCE
Harmonic Distortion (HD2/HD3)
Input Voltage Noise
Input Current Noise
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift
Input Bias Current
Conditions
Min
Input Common-Mode Voltage Range
Common-Mode Rejection
OUTPUT CHARACTERISTICS
Output Overdrive Recovery Time
Output Voltage Swing
Turn-On/Turn-Off Time
Input Leakage Current
POWER SUPPLY
Operating Range
Quiescent Current per Amplifier
Powered Down Quiescent Current
Positive Power Supply Rejection
Negative Power Supply Rejection
Unit
1050
200
390
≥410
60
60
870
9
MHz
MHz
MHz
MHz
MHz
MHz
V/µs
ns
f = 1 MHz, VOUT = 2 V p-p, RL = 1 kΩ
f = 10 MHz, VOUT = 2 V p-p, RL = 1 kΩ
f = 50 MHz, VOUT = 2 V p-p, RL = 1 kΩ
f = 100 kHz
f = 100 kHz
−113/−117
−90/−94
−64/−66
4
2.5
dBc
dBc
dBc
nV/√Hz
fA/√Hz
62
0.4
7
2
100
1
65
−77
500
1.3
0.1
−VS to +VS − 2.8
−90
GΩ
pF
pF
V
dB
8
−VS + 1.4 to
+VS − 1.3
−VS + 1 to
+VS − 1
40
100/170
ns
V
>+VS − 1
<+VS − 3
0.3/1
0.3
34
V
V
µs
µA
µA
Common mode
Common mode
Differential mode
VCM = ±0.5 V
VIN = ±2.5 V, G = 2
−VS + 1.5 to
+VS − 1.5
−VS + 1.1 to
+VS − 1.1
RL = 1 kΩ
Linear Output Current
Short-Circuit Current
POWER-DOWN
PD Pin Voltage
Max
VOUT = 0.1 V p-p
VOUT = 2 V p-p
VOUT = 0.1 V p-p, G = 2
VOUT = 0.1 V p-p
VIN = 3.3 V p-p, G = 2
VOUT = 2 V p-p, RL = 100 Ω, G = 2
VOUT = 4 V step
VOUT = 2 V step, G = 2
TMIN to TMAX
Input Bias Offset Current
Open-Loop Gain
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
Typ
1% output error
Sinking/sourcing
Enabled
Powered down
PD = +VS
PD = −VS
5
+VS = 4.5 V to 5.5 V, −VS = −5 V
+VS = 5 V, −VS = −4.5 V to −5.5 V
Rev. B | Page 3 of 28
−67
−67
19
1.5
−72
−72
2
20
mV
µV/°C
pA
pA
pA
dB
V
mA
mA
3
61
10
21
3
V
mA
mA
dB
dB
ADA4817-1/ADA4817-2
Data Sheet
5 V OPERATION
TA = 25°C, +VS = 3 V, −VS = −2 V, G = 1, RF = 348 Ω for G > 1, RL = 100 Ω to ground, unless otherwise noted.
Table 2.
Parameter
DYNAMIC PERFORMANCE
–3 dB Bandwidth
Full Power Bandwidth
0.1 dB Flatness
Slew Rate
Settling Time to 0.1%
NOISE/HARMONIC PERFORMANCE
Harmonic Distortion (HD2/HD3)
Input Voltage Noise
Input Current Noise
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift
Input Bias Current
Conditions
Min
Input Common-Mode Voltage Range
Common-Mode Rejection
OUTPUT CHARACTERISTICS
Output Overdrive Recovery Time
Output Voltage Swing
Turn-On/Turn-Off Time
Input Leakage Current
POWER SUPPLY
Operating Range
Quiescent Current per Amplifier
Powered Down Quiescent Current
Positive Power Supply Rejection
Negative Power Supply Rejection
Unit
500
160
280
95
32
320
11
MHz
MHz
MHz
MHz
MHz
V/µs
ns
f = 1 MHz, VOUT = 1 V p-p, RL = 1 kΩ
f = 10 MHz, VOUT = 1 V p-p, RL = 1 kΩ
f = 50 MHz, VOUT = 1 V p-p, RL = 1 kΩ
f = 100 kHz
f = 100 kHz
−87/−88
−68/−66
−57/−55
4
2.5
dBc
dBc
dBc
nV/√Hz
fA/√Hz
61
0.5
7
2
100
1
63
−72
500
1.3
0.1
−VS to +VS − 2.9
−83
GΩ
pF
pF
V
dB
13
−VS + 1 to
+VS − 1.2
−VS + 0.9 to
+VS − 1
20
40/130
ns
V
>+VS − 1
<+VS − 3
0.2/0.7
0.2
31
V
V
µs
µA
µA
Common mode
Common mode
Differential mode
VCM = ±0.25 V
VIN = ±1.25 V, G = 2
RL = 100 Ω
RL = 1 kΩ
Linear Output Current
Short-Circuit Current
POWER-DOWN
PD Pin Voltage
Max
VOUT = 0.1 V p-p
VOUT = 1 V p-p
VOUT = 0.1 V p- p, G = 2
VIN = 1 V p-p, G = 2
VOUT = 1 V p-p, G = 2
VOUT = 2 V step
VOUT = 1 V step, G = 2
TMIN to TMAX
Input Bias Offset Current
Open-Loop Gain
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
Typ
−VS + 1.3 to
+VS − 1.3
−VS + 1 to
+VS − 1.1
1% output error
Sinking/sourcing
Enabled
Powered down
PD = +VS
PD = −VS
5
+VS = 4.75 V to 5.25 V, −VS = 0 V
+VS = 5 V, −VS = −0.25 V to +0.25 V
Rev. B | Page 4 of 28
−66
−63
14
1.5
−71
−69
2.3
20
mV
µV/°C
pA
pA
pA
dB
V
mA
mA
3
53
10
16
2.8
V
mA
mA
dB
dB
Data Sheet
ADA4817-1/ADA4817-2
ABSOLUTE MAXIMUM RATINGS
PD = Quiescent Power + (Total Drive Power – Load Power)
Table 3.
Rating
10.6 V
See Figure 4
−VS − 0.5 V to +VS + 0.5 V
±VS
−65°C to +125°C
−40°C to +105°C
300°C
150°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, θJA is
specified for a device soldered in the circuit board for the
surface-mount packages.
V V
PD = (VS × I S ) +  S × OUT
RL
 2
PD = (VS × I S ) +
θJC
29
29
14
(VS /4 )2
(3)
RL
In single-supply operation with RL referenced to −VS, the worstcase situation is VOUT = VS/2.
Airflow increases heat dissipation, effectively reducing θJA.
More metal directly in contact with the package leads and
exposed paddle from metal traces, throughholes, ground,
and power planes also reduces θJA.
Figure 4 shows the maximum safe power dissipation in the
package vs. the ambient temperature for the exposed paddle
LFCSP_VD (single 94°C/W), SOIC_N_EP (single 79°C/W)
and LFCSP_WQ (dual 64°C/W) package on a JEDEC standard
4-layer board. θJA values are approximations.
3.5
MAXIMUM POWER DISSIPATION (W)
θJA
94
79
64
(2)
Consider RMS output voltages. If RL is referenced to −VS, as
in single-supply operation, the total drive power is VS × IOUT. If
the rms signal levels are indeterminate, consider the worst-case
scenario, when VOUT = VS/4 for RL to midsupply.
Table 4.
Package Type
LFCSP_VD (ADA4817-1)
SOIC_N_EP (ADA4817-1)
LFCSP_WQ (ADA4817-2)
 V
 – OUT

RL

Unit
°C/W
°C/W
°C/W
MAXIMUM SAFE POWER DISSIPATION
The maximum safe power dissipation for the ADA4817-1/
ADA4817-2 are limited by the associated rise in junction
temperature (TJ) on the die. At approximately 150°C (which is
the glass transition temperature), the properties of the plastic
change. Even temporarily exceeding this temperature limit may
change the stresses that the package exerts on the die, permanently
shifting the parametric performance of the ADA4817-x. Exceeding
a junction temperature of 175°C for an extended period can result
in changes in silicon devices, potentially causing degradation or
loss of functionality.
3.0
ADA4817-2, LFCSP
2.5
ADA4817-1, SOIC
2.0
1.5
ADA4817-1, LFCSP
1.0
0.5
0
–40 –30 –20 –10 0
10 20 30 40 50 60 70 80 90 100
AMBIENT TEMPERATURE (°C)
07756-008
Parameter
Supply Voltage
Power Dissipation
Common-Mode Input Voltage
Differential Input Voltage
Storage Temperature Range
Operating Temperature Range
Lead Temperature (Soldering, 10 sec)
Junction Temperature
(1)
2
Figure 4. Maximum Safe Power Dissipation vs. Ambient Temperature for
a 4-Layer Board
ESD CAUTION
The power dissipated in the package (PD) is the sum of the
quiescent power dissipation and the power dissipated in the
die due to the ADA4817-1/ADA4817-2 drive at the output.
The quiescent power is the voltage between the supply pins (VS)
multiplied by the quiescent current (IS).
Rev. B | Page 5 of 28
ADA4817-1/ADA4817-2
Data Sheet
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
ADA4817-1
PD 1
8 +VS
FB 2
7 OUT
–IN 3
6 NC
+IN 4
5 –VS
NC = NO CONNECT
NOTES
1. EXPOSED PAD CAN BE CONNECTED
TO GROUND PLANE OR NEGATIVE
SUPPLY PLANE.
07756-005
TOP VIEW
(Not to Scale)
Figure 5. ADA4817-1 Pin Configuration (8-Lead LFCSP)
Table 5. ADA4817-1 Pin Function Descriptions (8-Lead LFCSP)
Pin No.
1
2
3
4
5
6
7
8
Mnemonic
PD
FB
−IN
+IN
−VS
NC
OUT
+VS
Exposed pad (EPAD)
Description
Power-Down. Do not leave floating.
Feedback Pin.
Inverting Input.
Noninverting Input.
Negative Supply.
No Connect.
Output.
Positive Supply.
Exposed Pad. Can be connected to GND, −VS plane, or left floating.
ADA4817-1
FB 1
8
PD
–IN 2
7
+VS
+IN 3
6
OUT
–VS 4
5
NC
NC = NO CONNECT
07756-006
TOP VIEW
(Not to Scale)
NOTES
1. EXPOSED PAD CAN BE CONNECTED
TO GROUND PLANE OR NEGATIVE
SUPPLY PLANE.
Figure 6. ADA4817-1 Pin Configuration (8-Lead SOIC)
Table 6. ADA4817-1 Pin Function Descriptions (8-Lead SOIC)
Pin No.
1
2
3
4
5
6
7
8
Mnemonic
FB
−IN
+IN
−VS
NC
OUT
+VS
PD
Exposed pad (EPAD)
Description
Feedback Pin.
Inverting Input.
Noninverting Input.
Negative Supply.
No Connect.
Output.
Positive Supply.
Power-Down. Do not leave floating.
Exposed Pad. Can be connected to GND, −VS plane, or left floating.
Rev. B | Page 6 of 28
Data Sheet
ADA4817-1/ADA4817-2
ADA4817-2
–IN1 1
12 –VS1
+IN1 2
11 NC
FB2 8
9 –IN2
PD2 7
10 +IN2
–VS2 4
OUT2 5
+VS2 6
NC 3
NC = NO CONNECT
NOTES
1. EXPOSED PAD CAN BE CONNECTED
TO THE GROUND PLANE OR NEGATIVE
SUPPLY PLANE.
07756-107
14 +VS1
13 OUT1
16 FB1
15 PD1
TOP VIEW
(Not to Scale)
Figure 7. ADA4817-2 Pin Configuration (16-Lead LFCSP)
Table 7. 16-Lead LFCSP Pin Function Descriptions
Pin No.
1
2
3, 11
4
5
6
7
8
9
10
12
13
14
15
16
Mnemonic
−IN1
+IN1
NC
−VS2
OUT2
+VS2
PD2
FB2
−IN2
+IN2
−VS1
OUT1
+VS1
PD1
FB1
Exposed pad (EPAD)
Description
Inverting Input 1.
Noninverting Input 1.
No Connect.
Negative Supply 2.
Output 2.
Positive Supply 2.
Power-Down 2. Do not leave floating.
Feedback Pin 2.
Inverting Input 2.
Noninverting Input 2.
Negative Supply 1.
Output 1.
Positive Supply 1.
Power-Down 1. Do not leave floating.
Feedback Pin 1.
Exposed Pad. Can be connected to GND, −VS plane, or left floating.
Rev. B | Page 7 of 28
ADA4817-1/ADA4817-2
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VS = ±5 V, G = 1, (RF = 348 Ω for G > 1), RL = 100 Ω to ground, small signal VOUT = 100 mV p-p, large signal VOUT = 2 V p-p,
unless noted otherwise.
6
G =2
0
G=5
–3
–6
–9
–12
100k
1M
10M
100M
FREQUENCY (Hz)
1G
10G
G=2
G = 1, SINGLE
G = 1, DUAL
0
G=5
–3
–6
–9
–12
100k
Figure 8. Small Signal Frequency Response for Various Gains (LFCSP)
6
3
1M
10M
100M
FREQUENCY (Hz)
1G
10G
07756-009
3
G = 1, SINGLE
NORMALIZED CLOSED-LOOP GAIN (dB)
G = 1, DUAL
07756-066
NORMALIZED CLOSED-LOOP GAIN (dB)
6
Figure 11. Large Signal Frequency Response for Various Gains
6
VS = 10V, SOIC
VS = 10V, LFCSP
3
VS = 5V, LFCSP
CLOSED-LOOP GAIN (dB)
VS = 5V, SOIC
0
–3
–6
VS = 5V
–6
–9
1M
10M
100M
FREQUENCY (Hz)
1G
10G
VOUT = 1V p-p
–12
100k
1M
07756-007
–12
100k
9
CL = 6.6pF
CL = 4.4pF
10M
100M
FREQUENCY (Hz)
1G
10G
Figure 12. Large Signal Frequency Response for Various Supplies
Figure 9. Small Signal Frequency Response for Various Supplies
9
CL = 2.2pF
RF = 348Ω
RF = 274Ω
6
6
CLOSED-LOOP GAIN (dB)
CL = 0pF
3
0
–3
RF = 200Ω
3
0
–3
–6
–6
G=2
RF = 274Ω
–9
100k
1M
10M
100M
FREQUENCY (Hz)
1G
10G
07756-068
CLOSED-LOOP GAIN (dB)
–3
07756-010
–9
VS = 10V
0
G=2
–9
100k
1M
10M
100M
FREQUENCY (Hz)
1G
Figure 13. Small Signal Frequency Response for Various RF
Figure 10. Small Signal Frequency Response for Various CL
Rev. B | Page 8 of 28
10G
07756-011
CLOSED-LOOP GAIN (dB)
3
Data Sheet
ADA4817-1/ADA4817-2
6
G = 2, SS
3
CLOSED-LOOP GAIN (dB)
G = 2, LS
0.2
0.1
G = 1, SS
0
G = 1, LS
–0.1
–0.2
–0.3
–3
–6
–9
–0.4
–0.5
100k
1M
10M
100M
FREQUENCY (Hz)
1G
10G
–12
100k
–40
–40
–60
–60
DISTORTION (dBc)
–20
–80
HD2, RL = 1kΩ
–100
HD3, RL = 100Ω
–120
10M
100M
FREQUENCY (Hz)
Figure 15. Distortion vs. Frequency for Various Loads, VOUT = 2 V p-p
100M
1G
10G
HD2, VS = 5V
–80
–100
–120
HD2, VS = 10V
–140
100k
07756-014
1M
10M
HD3, VS = 5V
HD3, RL = 1kΩ
–140
100k
1M
Figure 17. Small Signal Frequency Response vs. Temperature
–20
HD2, RL = 100Ω
TA = +25°C, SINGLE
TA = +25°C, DUAL
TA = –40°C, SINGLE
TA = –40°C, DUAL
TA = +105°C, SINGLE
TA = +105°C, DUAL
FREQUENCY (Hz)
Figure 14. 0.1 dB Flatness Frequency Response vs. Gain and Output Voltage
DISTORTION (dBc)
0
07756-036
0.3
HD3, VS = 10V
1M
100M
10M
FREQUENCY (Hz)
07756-013
0.4
07756-012
NORMALIZED CLOSED-LOOP GAIN (dB)
0.5
Figure 18. Distortion vs. Frequency for Various Supplies, VOUT = 2 V p-p
–20
–20
fC = 1MHz
–40
HD2, VS = 5V
–60
DISTORTION (dBc)
DISTORTION (dBc)
–40
HD2, VS = 10V
–80
–100
–60
–80
HD2, RL = 100Ω
HD2, RL = 1kΩ
–100
HD3, VS = 5V
HD3, VS = 10V
1M
10M
FREQUENCY (Hz)
100M
Figure 16. Distortion vs. Frequency for Various Supplies, G = 2, VOUT = 2 V p-p
Rev. B | Page 9 of 28
–140
HD3, RL = 100Ω
HD3, RL = 1kΩ
0
1
2
3
4
5
OUTPUT VOLTAGE (V p-p)
Figure 19. Distortion vs. Output Voltage for Various Loads
6
07756-017
–140
100k
–120
07756-016
–120
ADA4817-1/ADA4817-2
0.15
DUAL, CF = 0.5pF
SINGLE, NO CF
0.10
SINGLE
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
0.10
DUAL, CF = 0.5pF
SINGLE, NO CF
0.05
0
–0.05
DUAL
–0.10
SINGLE
0.05
0
–0.05
DUAL
07756-018
–0.10
G=2
–0.15
–0.15
07756-021
0.15
Data Sheet
VS = 5V
G=2
TIME (5ns/DIV)
TIME (5ns/DIV)
Figure 20. Small Signal Transient Response
Figure 23. Small Signal Transient Response
1.5
0.075
1.0
0
–0.025
DUAL, LFCSP
RF = 0Ω
RL = 100Ω
VS = ±5V
G = +1
0
–0.5
–1.0
SINGLE, LFCSP
07756-022
–0.050
0.5
SINGLE, SOIC
–0.075
SINGLE, LFCSP
–1.5
TIME (5ns/DIV)
TIME (5ns/DIV)
Figure 21. Small Signal Transient Response vs. Package
Figure 24. Large Signal Transient Response
6
0.5
2 × VIN
SETTLING TIME
0.4
4
SETTLING TIME (%)
0.3
2
0
–2
VOUT
0.2
0.1
0
–0.1
–0.2
07756-023
–0.3
–4
TIME (10ns/DIV)
07756-019
–0.4
G=2
–6
SINGLE,SOIC
DUAL, LFCSP
RF = 0Ω
RL = 100Ω
VS = ±5V
G = +1
07756-024
OUTPUT VOLTAGE (V)
0.025
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
0.050
–0.5
TIME (5ns/DIV)
Figure 25. 0.1% Short-Term Settling Time
Figure 22. Output Overdrive Recovery
Rev. B | Page 10 of 28
Data Sheet
ADA4817-1/ADA4817-2
0.5
–10
0.4
–20
0.3
–40
–PSRR
+PSRR
–50
–60
–70
0.2
0.1
0
–0.1
–0.2
–80
–0.3
–90
–0.4
1M
10M
1G
100M
FREQUENCY (Hz)
–0.5
–40
07756-032
–100
100k
20
60
40
80
100
Figure 29. Offset Voltage vs. Temperature
INPUT VOLTAGE NOISE (nV/ Hz)
1000
1M
10M
100M
1G
FREQUENCY (Hz)
100
10
1
10
07756-029
CMRR (dB)
0
TEMPERATURE (°C)
Figure 26. PSRR vs. Frequency
–20
–25
–30
–35
–40
–45
–50
–55
–60
–65
–70
–75
–80
–85
–90
–95
–100
100k
–20
100
1k
10k
100k
1M
10M
100M
80
100
FREQUENCY (Hz)
07756-026
PSRR (dB)
–30
07756-037
OFFSET VOLTAGE (mV)
0
Figure 30. Input Voltage Noise
Figure 27. CMRR vs. Frequency
100
24
VS = ±5V
SUPPLY CURRENT (mA)
10
1
0.1
20
18
16
VS = +5V
14
0.01
100k
1M
10M
100M
FREQUENCY (Hz)
Figure 28. Output Impedance vs. Frequency
1G
10
–40
07756-033
12
07756-030
OUTPUT IMPEDANCE (Ω)
22
–20
0
20
40
60
TEMPERATURE (°C)
Figure 31. Quiescent Current vs. Temperature for Various Supply Voltages
Rev. B | Page 11 of 28
ADA4817-1/ADA4817-2
VS = ±5V
RL = 100Ω
1.5
–V-S + VOUT
700
NUMBER OF HITS
1.4
1.3
+VS – VOUT
+VS – VOUT
1.2
1.1
1.0
500
400
300
0.8
–40
–20
0
20
40
60
100
80
0
–1.5
100
0
70
60
GAIN
40
PHASE
–90
30
20
10
PHASE (Degrees)
–45
50
–135
100M
–180
1G
FREQUENCY (Hz)
07756-015
0
10M
–0.5
0
0.5
1.0
Figure 34. Input Offset Voltage Histogram
Figure 32. Output Saturation Voltage vs. Temperature
1M
–1.0
VOS (mV)
TEMPERATURE (°C)
100k
07756-025
VS = +5V
0.9
–10
10k
600
200
–VS + VOUT
GAIN (dB)
N: 4197
MEAN: –0.0248457
SD: 0.245658
800
07756-034
OUTPUT SATURATION VOLTAGE (V)
1.6
Data Sheet
Figure 33. Open-Loop Gain and Phase vs. Frequency
Rev. B | Page 12 of 28
1.5
Data Sheet
ADA4817-1/ADA4817-2
TEST CIRCUITS
The output feedback pins are used for ease of layout as shown in Figure 35 to Figure 40.
+VS
+VS
10µF
+
10µF
+
RG
0.1µF
RF
0.1µF
0.1µF
0.1µF
VOUT
VOUT
VIN
VIN
RL
49.9Ω
RL
49.9Ω
10µF
+
–VS
–VS
Figure 35. G = 1 Configuration
Figure 38. Noninverting Gain Configuration
+VS
+VS
10µF
+
49.9Ω
AC
0.1µF
07756-147
0.1µF
07756-141
+
10µF
0.1µF
VOUT
VOUT
RL
49.9Ω
RL
+
07756-145
0.1µF
–VS
07756-148
AC
10µF
–VS
Figure 36. Positive Power Supply Rejection
Figure 39. Negative Power Supply Rejection
+VS
+VS
10µF
10µF
+
+
1kΩ
RF
0.1µF
RSNUB
VIN
49.9Ω
0.1µF
VOUT
CL
0.1µF
1kΩ
VIN
RL
1kΩ
53.6Ω
10µF
0.1µF
VOUT
RL
1kΩ
–VS
+
07756-142
+
10µF
0.1µF
0.1µF
–VS
Figure 37. Capacitive Load Configuration
Figure 40. Common-Mode Rejection
Rev. B | Page 13 of 28
07756-146
RG
ADA4817-1/ADA4817-2
Data Sheet
THEORY OF OPERATION
The ADA4817-1/ADA4817-2 are voltage feedback operational
amplifiers that combine new architecture for FET input operational
amplifiers with the eXtra Fast Complementary Bipolar (XFCB)
process from Analog Devices, resulting in an outstanding
combination of speed and low noise. The innovative high speed
FET input stage handles common-mode signals from the negative
supply to within 2.7 V of the positive rail. This stage is combined
with an H-bridge to attain a 870 V/μs slew rate and low distortion,
in addition to 4 nV/√Hz input voltage noise. The amplifier
features a high speed output stage capable of driving heavy loads
sourcing and sinking up to 40 mA of linear current. Supply current
and offset current are laser trimmed for optimum performance.
These specifications make the ADA4817-1/ ADA4817-2 a great
choice for high speed instrumentation and high resolution data
acquisition systems. Its low noise, picoamp input current, precision
offset, and high speed make them superb preamps for fast photodiode applications.
Closed-loop −3 dB frequency
f −3dB = f CROSSOVER ×
Solving for the transfer function,
−2π × f CROSSOVER × R F
VO
=
VI (R F + RG )S + 2π × f CROSSOVER × RG
At dc
(7)
VO
R
=− F
RG
VI
(8)
Solve for closed-loop −3 dB frequency by,
f −3dB = f CROSSOVER ×
RG
R F + RG
(9)
A = (2π × fCROSSOVER )/s
80
OPEN-LOOP GAIN (A) (dB)
RF
(6)
INVERTING CLOSED-LOOP FREQUENCY RESPONSE
CLOSED-LOOP FREQUENCY RESPONSE
The ADA4817-1/ADA4817-2 are classic voltage feedback
amplifiers with an open-loop frequency response that can be
approximated as the integrator response shown in Figure 43. Basic
closed-loop frequency response for inverting and noninverting
configurations can be derived from the schematics shown in
Figure 41 and Figure 42.
RG
R F + RG
60
40
fCROSSOVER = 410MHz
20
RG
VOUT
RG
VOUT
07756-045
A
Figure 42. Inverting Configuration
Solving for the transfer function,
(4)
 R + RF
VOUT (error ) = I b + × RS  G
 RG
where fCROSSOVER is the frequency where the amplifier’s open-loop
gain equals 0 dB.
(5)

 − I b − × R F + VOS


 RG + R F 


 R

G


(10)
RF
+VOS –
RG
At dc,
VO RF + RG
=
VI
RG
1000
Figure 44 shows a voltage feedback amplifier’s dc errors. For
both inverting and noninverting configurations,
NONINVERTING CLOSED-LOOP FREQUENCY
RESPONSE
2π × f CROSSOVER (RG + R F )
VO
=
VI (R F + RG )S + 2π × f CROSSOVER × RG
100
The closed-loop bandwidth is inversely proportional to the noise
gain of the op amp circuit, (RF + RG)/RG. This simple model is
accurate for noise gains above 2. The actual bandwidth of circuits
with noise gains at or below 2 is higher than those predicted
with this model due to the influence of other poles in the
frequency response of the real op amp.
RF
VE
10
FREQUENCY (MHz)
Figure 43. Open-Loop Gain vs. Frequency and Basic Connections
Figure 41. Noninverting Configuration
VIN
1
0.1
07756-046
07756-044
0
VIN
RS
Ib –
A
VOUT
Ib+
Figure 44. Voltage Feedback Amplifier’s DC Errors
Rev. B | Page 14 of 28
07756-047
A
VE
VIN
Data Sheet
ADA4817-1/ADA4817-2
VOS = VOS nom +
Δ VS Δ VCM
+
PSR CMR
(11)
where:
VOSnom is the offset voltage specified at nominal conditions.
+VS
10µF
+
ΔVS is the change in power supply from nominal conditions.
PSR is the power supply rejection.
ΔVCM is the change in common-mode voltage from nominal
conditions.
CMR is the common-mode rejection.
Note that such capacitance introduces significant peaking in the
frequency response. Larger capacitance values can be driven but
must use a snubbing resistor (RSNUB) at the output of the amplifier,
as shown in Figure 45. Adding a small series resistor, RSNUB, creates
a zero that cancels the pole introduced by the load capacitance.
Typical values for RSNUB can range from 10 Ω to 50 Ω. The value is
typically based on the circuit requirements. Figure 45 also shows
another way to reduce the effect of the pole created by the capacitive
load (CL) by placing a capacitor (CF) in the feedback loop parallel
to the feedback resistor Typical capacitor values can range from
0.5 pF to 2 pF. Figure 46 shows the effect of adding a feedback
capacitor to the frequency response.
CF
WIDEBAND OPERATION
The distortion performance depends on a number of variables:
•
•
•
•
•
The closed-loop gain of the application
Whether it is inverting or noninverting
Amplifier loading
Signal frequency and amplitude
Board layout
The best performance is usually obtained in the G + 1
configuration with no feedback resistance, big output
load resistors, and small board parasitic capacitances.
DRIVING CAPACITIVE LOADS
In general, high speed amplifiers have a difficult time driving
capacitive loads. This is particularly true in low closed-loop
gains, where the phase margin is the lowest. The difficulty
arises because the load capacitance, CL, forms a pole with the
output resistance, RO, of the amplifier. The pole can be described
by the following equation:
fP =
1
2πRO C L
RF
RG
(12)
If this pole occurs too close to the unity-gain crossover point,
the phase margin degrades. This is due to the additional phase
loss associated with the pole.
0.1µF
RSNUB
VIN
49.9Ω
0.1µF
VOUT
CL
RL
10µF
+
The ADA4817-1/ADA4817-2 provides excellent performance as
a high speed buffer. Figure 41 shows the circuit used for wideband
characterization for high gains. The impedance at the summing
junction (RF || RG) forms a pole in the loop response of the amplifier with the amplifier’s input capacitance of 1.3 pF. This pole
can cause peaking and ringing if its frequency is too low. Feedback resistances of 100 Ω to 400 Ω are recommended because
they minimize the peaking and they do not degrade the
performance of the output stage. Peaking in the frequency
response can also be compensated for with a small feedback
capacitor (CF) in parallel with the feedback resistor, or a series
resistor in the noninverting input, as shown in Figure 45.
0.1µF
–VS
07756-143
The voltage error due to Ib+ and Ib– is minimized if RS = RF || RG
(though with the ADA4817-1/ADA4817-2 input currents in the
picoamp range, this is likely not a concern). To include commonmode effects and power supply rejection effects, total VOS can be
modeled by
Figure 45. RSNUB or CF Used to Reduce Peaking
THERMAL CONSIDERATIONS
With 10 V power supplies and 19 mA quiescent current, the
ADA4817-1/ADA4817-2 dissipate 190 mW with no load. This
implies that in the LFCSP, whose thermal resistance is 94°C/W for
the ADA4817-1 and 64°C/W for the ADA4817-2, the junction
temperature is typically almost 25° higher than the ambient temperature. The ADA4817-1/ADA4817-2 are designed to maintain a
constant bandwidth over temperature; therefore, an initial ramp up
of the current consumption during warm-up is expected. The VOS
temperature drift is below 8 µV/°C; therefore, it can change up to
0.3 mV due to warm-up effects for an ADA4817-1/ADA4817-2
in a LFCSP on 10 V. The input bias current increases by a factor
of 1.7 for every 10°C rise in temperature.
Heavy loads increase power dissipation and raise the chip
junction temperature as described in the Absolute Maximum
Ratings section. Take care not to exceed the rated power
dissipation of the package.
POWER-DOWN OPERATION
The ADA4817-1/ADA4817-2 are equipped with separate powerdown pins (PD) for each amplifier. This allows the user the ability
to reduce the quiescent supply current when an amplifier is
inactive from 19 mA to below 2 mA. The power-down threshold
levels are derived from the voltage applied to the +VS pin. In ±5 V
supply application, the enable voltage is greater than +4 V, and in a
+3 V, −2 V supply application, the enable voltage is greater than
+2 V. However, the amplifier is powered down whenever the
voltage applied to PD is 3 V below +VS. If the PD pin is not used,
connect it to the positive supply to ensure proper start-up.
Rev. B | Page 15 of 28
ADA4817-1/ADA4817-2
Data Sheet
Table 8. Power-Down Voltage Control
PD Pin
±5 V
+3 V, −2 V
Not active
Active
>4 V
<2 V
>2 V
<0 V
Figure 47 shows the higher frequency attenuation, which
reduces the peaking but also reduces the −3 dB bandwidth.
6
CAPACITIVE FEEDBACK
RS = 75Ω
CF = 0.5pF
NO CF
0
RS = 100Ω
–3
–9
RL = 100Ω
VS = ±5V
VOUT = 0.1V p-p
G=1
1M
07756-247
–6
10M
100M
FREQUENCY (Hz)
1G
10G
Figure 47. Small Signal Frequency Response for Various RS (SOIC)
As shown in Figure 47, the peaking dropped by almost 2 dB
when RS = 0 Ω to RS = 100 Ω, and in return, the −3 dB bandwidth
dropped from 1 GHz to 700 MHz. To maintain the −3 dB
bandwidth and to reduce peaking, an RLC circuit is recommended
instead of RS, as shown in Figure 48.
L
CF = 1pF
3
C
10nH
2pF
R
0
120Ω
Figure 48. RLC Circuit
–3
–9
1M
10M
100M
1G
10G
FREQUENCY (Hz)
Figure 46. Small Signal Frequency Response vs. Feedback Capacitor
(ADA4817-2)
HIGHER FREQUENCY ATTENUATION
There is another package variation problem between the SOIC
and the LFCSP package. The SOIC package shows approximately
1 dB to 1.5 dB of additional peaking at a gain of 1. This is due to
the parasitic in the SOIC package, which is not recommended
for very high frequency parts that exceed 1 GHz. A good approach
to reducing the peaking is to place a resistor, RS, in series with
the noninverting input. This creates a first-order pole formed
by RS and CIN, the common-mode input capacitance.
The R in parallel to the series LC forms a notch that can be
shaped to compensate for the peaking produced by the amplifier.
The result is a smooth 1 GHz −3 dB bandwidth, 250 MHz 0.1 dB
flatness, and less than 1 dB of peaking. This circuit should be
placed in the path of the noninverting input when the ADA4817-x
is used at a gain of 1. The RLC values may need tweaking
depending on the source impedance and the flatness and bandwidth required. Figure 49 shows the frequency response after the
RLC circuit is in place.
6
NO RLC
3
0
RLC
–3
–6
–9
RL = 100Ω
VS = 10V
VOUT = 100mV p-p
G=1
1M
10M
07756-249
RF = 348Ω
G=2
VS = 10V
VOUT = 100mV p-p
RL = 100Ω
CLOSED-LOOP GAIN (dB)
–6
07756-049
CLOSED-LOOP GAIN (dB)
6
RS = 0Ω
07756-248
9
RS = 50Ω
3
CLOSED-LOOP GAIN (dB)
Due to package variations and pin-to-pin parasitics between the
single and the dual models, the ADA4817-2 has a little more
peaking then the ADA4817-1, especially at a gain of 2. The best
way to tame the peaking is to place a feedback capacitor across
the feedback resistor. Figure 46 shows the small signal frequency
response of the ADA4817-2 at a gain of 2 vs. CF. At first, no CF
was used to show the peaking, but then two other values of
0.5 pF and 1 pF were used to show how to reduce the peaking or
even eliminate it. As shown in Figure 46, if the power consumption
is a factor in the system, then using a larger feedback capacitor
is acceptable as long as a feedback capacitor is used across it to
control the peaking. However, if power consumption is not an
issue, then a lower value feedback resistor, such as 200 Ω, would
not require any additional feedback capacitance to maintain
flatness and lower peaking.
100M
FREQUENCY (Hz)
1G
Figure 49. Frequency Response with RLC Circuit
Rev. B | Page 16 of 28
10G
Data Sheet
ADA4817-1/ADA4817-2
LAYOUT, GROUNDING, AND BYPASSING CONSIDERATIONS
Laying out the PCB is usually the last step in the design process
and often proves to be one of the most critical. A brilliant design
can be rendered useless because of poor layout. Because the
ADA4817-1/ADA4817-2 can operate into the RF frequency
spectrum, high frequency board layout considerations must
be taken into account. The PCB layout, signal routing, power
supply bypassing, and grounding all must be addressed to
ensure optimal performance.
SIGNAL ROUTING
The ADA4817-1/ADA4817-2 feature the new low distortion
pinout with a dedicated feedback pin that allows a compact
layout. The dedicated feedback pin reduces the distance from
the output to the inverting input, which greatly simplifies the
routing of the feedback network.
When laying out the ADA4817-1/ADA4817-2 as a unity-gain
amplifier, it is recommended that a short, but wide, trace be
placed between the dedicated feedback pins, and the inverting
input to the amplifier be used to minimize stray parasitic
inductance.
To minimize parasitic inductances, use ground planes under
high frequency signal traces. However, remove the ground
plane from under the input and output pins to minimize the
formation of parasitic capacitors, which degrades phase margin.
Signals that are susceptible to noise pickup should be run on
the internal layers of the PCB, which can provide maximum
shielding.
POWER SUPPLY BYPASSING
Power supply bypassing is a critical aspect of the PCB design
process. For best performance, the ADA4817-1/ADA4817-2
power supply pins need to be properly bypassed.
A parallel connection of capacitors from each of the power
supply pins to ground works best. Paralleling different values
and sizes of capacitors helps to ensure that the power supply
pins see a low ac impedance across a wide band of frequencies.
This is important for minimizing the coupling of noise into the
amplifier. Starting directly at the power supply pins, place the
smallest value and sized component on the same side of the
board as the amplifier, and as close as possible to the amplifier,
and connect it to the ground plane. Repeat this process for the
next largest value capacitor. It is recommended that a 0.1 µF
ceramic, 0508 case be used for the ADA4817-1/ADA4817-2.
The 0508 offers low series inductance and excellent high
frequency performance. The 0.1 µF provides low impedance at
high frequencies. Place a 10 µF electrolytic capacitor in parallel
with the 0.1 µF. The 10 µF capacitor provides low ac impedance
at low frequencies. Smaller values of electrolytic capacitors can
be used depending on the circuit requirements. Additional
smaller value capacitors help to provide a low impedance path
for unwanted noise out to higher frequencies but are not always
necessary.
Placement of the capacitor returns (grounds) is also important.
Returning the capacitors’ grounds close to the amplifier load is
critical for distortion performance. Keeping the capacitors distance
short but equal from the load is optimal for performance.
In some cases, bypassing between the two supplies can help
to improve PSRR and to maintain distortion performance in
crowded or difficult layouts. This is another option to improve
performance.
Minimizing the trace length and widening the trace from the
capacitors to the amplifier reduces the trace inductance. A series
inductance with the parallel capacitance can form a tank circuit,
which can introduce high frequency ringing at the output. This
additional inductance can also contribute to increased distortion
due to high frequency compression at the output. The use of
vias should be minimized in the direct path to the amplifier power
supply pins because vias can introduce parasitic inductance, which
can lead to instability. When required to use vias, choose multiple
large diameter vias because this lowers the equivalent parasitic
inductance.
GROUNDING
The use of ground and power planes is encouraged as a method
of providing low impedance returns for power supply and signal
currents. Ground and power planes can also help to reduce stray
trace inductance and to provide a low thermal path for the
amplifier. Do not use ground and power planes under any of
the pins. The mounting pads and the ground or power planes
can form a parasitic capacitance at the input of the amplifier. Stray
capacitance on the inverting input and the feedback resistor form
a pole, which degrades the phase margin, leading to instability.
Excessive stray capacitance on the output also forms a pole,
which degrades phase margin.
EXPOSED PADDLE
The ADA4817-1/ADA4817-2 feature an exposed paddle, which
lowers the thermal resistance by 25% compared to a standard
SOIC plastic package. The exposed paddle of the ADA4817-1/
ADA4817-2 floats internally which provides the maximum
flexibility and ease of use. It can be connected to the ground plane
or to the negative power supply plane. In cases where thermal
heating is not an issue, the exposed pad can be left floating.
The use of thermal vias or heat pipes can also be incorporated
into the design of the mounting pad for the exposed paddle.
These additional vias help to lower the overall junction-toambient temperature (θJA). Using a heavier weight copper on
the surface to which the exposed paddle of the amplifier is
soldered can greatly reduce the overall thermal resistance seen
by the ADA4817-1/ADA4817-2.
Rev. B | Page 17 of 28
ADA4817-1/ADA4817-2
Data Sheet
LEAKAGE CURRENTS
INPUT CAPACITANCE
Poor PCB layout, contaminants, and the board insulator
material can create leakage currents that are much larger than
the input bias current of the ADA4817-1/ADA4817-2. Any
voltage differential between the inputs and nearby runs sets
up leakage currents through the PCB insulator, for example, 1 V/
100 GΩ = 10 pA. Similarly, any contaminants, such as skin oils
on the board, can create significant leakage. To reduce leakage
significantly, put a guard ring (shield) around the inputs and
input leads that are driven to the same voltage potential as the
inputs. This way there is no voltage potential between the inputs
and surrounding area to set up any leakage currents. For the
guard ring to be completely effective, it must be driven by a
relatively low impedance source and should completely
surround the input leads on all sides (above and below)
while using a multilayer board.
Along with bypassing and ground, high speed amplifiers can be
sensitive to parasitic capacitance between the inputs and ground. A
few picofarads of capacitance reduces the input impedance at high
frequencies, in turn increasing the gain of the amplifier, causing
peaking of the frequency response or even oscillations if severe
enough. It is recommended that the external passive components
connected to the input pins be placed as close as possible to the
inputs to avoid parasitic capacitance. The ground and power
planes must be kept at a small distance from the input pins on
all layers of the board.
Another effect that can cause leakage currents is the charge
absorption of the insulator material itself. Minimizing the amount
of material between the input leads and the guard ring helps to
reduce the absorption. In addition, low absorption materials,
such as Teflon® or ceramic, can be necessary in some instances.
INPUT-TO-INPUT/OUTPUT COUPLING
To minimize capacitive coupling between the inputs and outputs,
the output signal traces should not be parallel with the inputs.
In addition, the input traces should not be close to each other. A
minimum of 7 mils between the two inputs is recommended.
Rev. B | Page 18 of 28
Data Sheet
ADA4817-1/ADA4817-2
APPLICATIONS INFORMATION
The ADA4817-1/ADA4817-2 feature a new low distortion
pinout from Analog Devices. The new pinout provides two
advantages over the traditional pinout. The first advantage is
improved second harmonic distortion performance, which is
accomplished by the physical separation of the noninverting
input pin and the negative power supply pin. The second
advantage is the simplification of the layout due to the dedicated
feedback pin and easy routing of the gain set resistor back to
the inverting input pin. This allows a compact layout, which
helps to minimize parasitics and increase stability.
The designer does not need to use the dedicated feedback pin to
provide feedback for the ADA4817-1/ADA4817-2. The output
pin of the ADA4817-1/ADA4817-2 can still be used to provide
feedback to the inverting input of the ADA4817-1/ADA4817-2.
WIDEBAND PHOTODIODE PREAMP
The wide bandwidth and low noise of the ADA4817-1/
ADA4817-2 make it an ideal choice for transimpedance
amplifiers, such as those used for signal conditioning with
high speed photodiodes. Figure 50 shows an I/V converter
with an electrical model of a photodiode. The basic transfer
function is
I
 RF
VOUT  PHOTO
(13)
1  sC F R F
where:
IPHOTO is the output current of the photodiode.
The parallel combination of RF and CF sets the signal bandwidth.
The stable bandwidth attainable with this preamp is a function
of RF, the gain bandwidth product of the amplifier, and the total
capacitance at the summing junction of the amplifier, including the
photodiode capacitance (CS) and the amplifier input capacitance.
RF and the total capacitance produce a pole in the amplifier’s
loop transmission that can result in peaking and instability.
Adding CF creates a zero in the loop transmission that compensates for the effect of the pole and reduces the signal bandwidth.
It can be shown that the signal bandwidth obtained with a 45°
phase margin (f(45)) is defined by
f CR
2  R F  (C S  C M  C D )
f ( 45) 
where:
fCR is the amplifier crossover frequency.
RF is the feedback resistor.
CS is the source capacitance including the photodiode and the
board parasitic.
CM is the common-mode capacitance of the amplifier.
CD is the differential capacitance of the amplifier.
The value of CF that produces f(45) can be shown to be
CF 
CS  C M  CD
2  R F  f CR
The preamplifier output noise over frequency is shown in
Figure 51.
VOLTAGE NOISE (nV/ Hz)
RF
CM
RSH = 1011Ω
CS
CD
VOUT
07756-048
CM
VB
(15)
The frequency response shows less peaking if bigger CF values
are used.
CF
IPHOTO
(14)
Figure 50. Wideband Photodiode Preamp
f1 =
1
2 RF (CF + CS + CM + CD)
f2 =
1
2 RFCF
f3 =
fCR
(CF + CS + CM + CD)/CF
RF NOISE
VEN (CF + CS + CM + CD)/CF
f3
f2
f1
VEN
NOISE DUE TO AMPLIFIER
FREQUENCY (Hz)
Figure 51. Photodiode Voltage Noise Contributions
Rev. B | Page 19 of 28
07756-043
LOW DISTORTION PINOUT
ADA4817-1/ADA4817-2
Data Sheet
The loop transmission zero introduced by CF limits the
amplification. The noise gain bandwidth extends past the preamp signal bandwidth and is eventually rolled off by the decreasing
loop gain of the amplifier. The current equivalent noise from the
inverting terminal is typically negligible for most applications.
The innovative architecture used in the ADA4817-1/ADA4817-2
makes balancing both inputs unnecessary, as opposed to traditional
FET input amplifiers. Therefore, minimizing the impedance
seen from the noninverting terminal to ground at all frequencies
is critical for optimal noise performance.
45
40
35
MAGNITUDE (dB)
30
25
20
15
10
5
07756-051
G = 63V/V
R = 100Ω
0 V L = 10V
S
VOUT = 6V p-p
–5
0.1
1
10
100
1000
FREQUENCY (MHz)
Figure 52. Photodiode Preamp Frequency Response
The pole in the loop transmission translates to a zero in the
noise gain of the amplifier, leading to an amplification of the
input voltage noise over frequency.
Integrating the square of the output voltage noise spectral density
over frequency and then taking the square root allows users
to obtain the total rms output noise of the preamp. Table 9
summarizes approximations for the amplifier and feedback
and source resistances. Noise components for an example
preamp with RF = 50 kΩ, CS = 30 pF, and CF = 0.5 pF
(bandwidth of about 6.4 MHz) are also listed.
Table 9. RMS Noise Contributions of Photodiode Preamp
Contributor
RF
VEN Amp
IEN Amp
Expression
RMS Noise with RF = 50 kΩ, CS = 30 pF, CF = 0.5 pF
94 µV
4 kT × R F × f 2 × 1.57
VEN ×
777.5 µV
CS + CM + C D + CF
× f 3 × 1.57
CF
0.4 µV
IEN × R F × f 2 × 1.57
783 µV (total)
Rev. B | Page 20 of 28
Data Sheet
ADA4817-1/ADA4817-2
Common-mode rejection of the in-amp is primarily determined by
the match of resistor ratios, R1:R2 to R3:R4. It can be estimated by
HIGH SPEED JFET INPUT INSTRUMENTATION
AMPLIFIER
VO
(δ1 − δ2 )
=
VCM (1 + δ1) δ2
Figure 53 shows an example of a high speed instrumentation
amplifier with a high input impedance using the ADA4817-1/
ADA4817-2. The dc transfer function is
 2R
VOUT = (VN − VP ) 1 + F
RG





(17)
The summing junction impedance for the preamps is equal
to RF || 0.5(RG). Keep this value relatively low to improve the
bandwidth response like in the previous example.
(16)
For G = 1, it is recommended that the feedback resistors for the
two preamps be set to 0 Ω and the gain resistor be open. The
system bandwidth for G = 1 is 400 MHz. For gains higher than 2,
the bandwidth is set by the preamp, and it can be approximated by
In-amp−3 dB = (fCR × RG)/(2 × RF)
VCC
0.1µF
10µF
RS1
VN
R2
350Ω
ADA4817-2
U1
0.1µF
VCC
10µF
VEE
0.1µF
R1
350Ω
10µF
RF = 500Ω
VO
ADA4817-1
RG
R3
350Ω
RF = 500Ω
0.1µF
10µF
VCC
R4
350Ω
0.1µF
VEE
10µF
ADA4817-2
U2
0.1µF
VP
10µF
07756-050
RS2
VEE
Figure 53. High Speed Instrumentation Amplifier
Rev. B | Page 21 of 28
ADA4817-1/ADA4817-2
Data Sheet
Resistor values are kept low for minimal noise contribution,
offset voltage, and optimal frequency response. Due to the low
capacitance values used in the filter circuit, the PCB layout and
minimization of parasitics is critical. A few picofarads can detune
the corner frequency, fc, of the filter. The capacitor values shown
in Figure 55 actually incorporate some stray PCB capacitance.
ACTIVE LOW-PASS FILTER (LPF)
Active filters are used in many applications such as antialiasing
filters and high frequency communication IF strips.
With a 410 MHz gain bandwidth product and high slew rate,
the ADA4817-1/ADA4817-2 is an ideal candidate for active
filters. Moreover, thanks to the low input bias current provided
by the FET stage, the ADA4817-1/ADA4817-2 eliminate any dc
errors. Figure 54 shows the frequency response of 90 MHz and
45 MHz LPFs. In addition to the bandwidth requirements, the slew
rate must be capable of supporting the full power bandwidth of the
filter. In this case, a 90 MHz bandwidth with a 2 V p-p output
swing requires at least 870 V/μs. This performance is achievable
at 90 MHz only because of the wide bandwidth and high slew
rate of the ADA4817-1/ADA4817-2.
The circuit shown in Figure 55 is a 4-pole, Sallen-Key, low-pass
filter (LPF). The filter comprises two identical cascaded SallenKey LPF sections, each with a fixed gain of G = 2. The net gain
of the filter is equal to G = 4 or 12 dB. The actual gain shown in
Figure 54 is 12 dB. This does not take into account the output
voltage being divided in half by the series matching termination
resistor, RT, and the load resistor.
Setting the resistors equal to each other greatly simplifies the
design equations for the Sallen-Key filter. To achieve 90 MHz
the value of R should be set to 182 Ω. However, if the value of R
is doubled, the corner frequency is cut in half to 45 MHz. This
would be an easy way to tune the filter by simply multiplying
the value of R (182 Ω) by the ratio of 90 MHz and the new
corner frequency in megahertz. Figure 54 shows the output of
each stage of the filter and the two different filters corresponding
to R = 182 Ω and R = 365 Ω. It is not recommended to increase
the corner frequency beyond 90 MHz due to bandwidth and
slew rate limitations unless unity-gain stages are acceptable.
15
12
9
6
3
0
–3
–6
–9
–12
–15
–18
–21
–24
–27
–30
–33
–36
–39
–42
100k
OUT2, f = 90MHz
OUT1, f = 90MHz
OUT1, f = 45MHz
OUT2, f = 45MHz
1M
C3
3.9pF
10µF
+5V
RT
49.9Ω
R
U1
R
R
C2
5.6pF
10µF
0.1µF
10µF
OUT1
U2
R
C4
5.6pF
0.1µF
RT
49.9Ω
10µF
OUT2
0.1µF
0.1µF
–5V
R2
348Ω
–5V
R1
348Ω
R4
348Ω
R3
348Ω
Figure 55. 4-Pole Sallen-Key Low-Pass Filter (ADA4817-2)
Rev. B | Page 22 of 28
07756-054
+IN1
100M
Figure 54. Low-Pass Filter Response
C1
3.9pF
+5V
10M
FREQUENCY (Hz)
1G
07756-062
MAGNITUDE (dB)
Capacitor selection is critical for optimal filter performance.
Capacitors with low temperature coefficients, such as NPO
ceramic capacitors and silver mica, are good choices for filter
elements.
Data Sheet
ADA4817-1/ADA4817-2
1.2
0.15
0.10
0.8
90MHz
90MHz
45MHz
45MHz
0.4
VOLTAGE (V)
0
0
–0.4
–0.05
–0.15
TIME (5ns/DIV)
–1.2
TIME (5ns/DIV)
Figure 57. Large Signal Transient Response (Low-Pass Filter)
Figure 56. Small Signal Transient Response (Low-Pass Filter)
Rev. B | Page 23 of 28
07756-064
–0.8
–0.10
07756-063
VOLTAGE (V)
0.05
ADA4817-1/ADA4817-2
Data Sheet
OUTLINE DIMENSIONS
0.60 MAX
0.50
BSC
0.60 MAX
5
2.95
2.75 SQ
2.55
TOP
VIEW
PIN 1
INDICATOR
8
4
12° MAX
0.05 MAX
0.01 NOM
0.30
0.23
0.18
SEATING
PLANE
1
0.50
0.40
0.30
0.70 MAX
0.65 TYP
0.90 MAX
0.85 NOM
1.60
1.45
1.30
EXPOSED
PAD
(BOTTOM VIEW)
1.89
1.74
1.59
PIN 1
INDICATOR
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
0.20 REF
04-04-2012-A
3.25
3.00 SQ
2.75
Figure 58. 8-Lead Lead Frame Chip Scale Package [LFCSP_VD]
3 mm × 3 mm Body, Very Thin, Dual Lead (CP-8-2)
Dimensions shown in millimeters
5.00
4.90
4.80
2.29
0.356
5
1
4
6.20
6.00
5.80
4.00
3.90
3.80
2.29
0.457
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
BOTTOM VIEW
1.27 BSC
3.81 REF
TOP VIEW
1.65
1.25
1.75
1.35
SEATING
PLANE
0.51
0.31
0.50
0.25
0.10 MAX
0.05 NOM
COPLANARITY
0.10
8°
0°
45°
0.25
0.17
1.04 REF
1.27
0.40
COMPLIANT TO JEDEC STANDARDS MS-012-A A
Figure 59. 8-Lead Standard Small Outline Package with Exposed Pad [SOIC_N_EP]
(RD-8-1)
Dimensions shown in millimeters and (inches)
Rev. B | Page 24 of 28
06-02-2011-B
8
Data Sheet
ADA4817-1/ADA4817-2
0.35
0.30
0.25
0.65
BSC
PIN 1
INDICATOR
16
13
1
12
EXPOSED
PAD
2.40
2.35 SQ
2.30
9
TOP VIEW
0.80
0.75
0.70
0.50
0.40
0.30
4
8
0.25 MIN
BOTTOM VIEW
0.05 MAX
0.02 NOM
COPLANARITY
0.08
0.20 REF
SEATING
PLANE
5
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
07-18-2012-B
PIN 1
INDICATOR
4.10
4.00 SQ
3.90
COMPLIANT TO JEDEC STANDARDS MO-220-WGGC-3.
Figure 60.16-Lead Lead Frame Chip Scale Package [LFCSP_WQ]
4 mm × 4 mm Body, Very Very Thin Quad (CP-16-20)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
ADA4817-1ACPZ-R2
ADA4817-1ACPZ-RL
ADA4817-1ACPZ-R7
ADA4817-1ACP-EBZ
Temperature Range
–40°C to +105°C
–40°C to +105°C
–40°C to +105°C
ADA4817-1ARDZ
ADA4817-1ARDZ-RL
ADA4817-1ARDZ-R7
ADA4817-1ARD-EBZ
–40°C to +105°C
–40°C to +105°C
–40°C to +105°C
ADA4817-2ACPZ-R2
ADA4817-2ACPZ-RL
ADA4817-2ACPZ-R7
ADA4817-2ACP-EBZ
–40°C to +105°C
–40°C to +105°C
–40°C to +105°C
1
Package Description
8-Lead LFCSP_VD
8-Lead LFCSP_VD
8-Lead LFCSP_VD
Evaluation Board for
8-Lead LFCSP
8-Lead SOIC_N_EP
8-Lead SOIC_N_EP
8-Lead SOIC_N_EP
Evaluation Board
for8-Lead SOIC
16-Lead LFCSP_WQ
16-Lead LFCSP_WQ
16-Lead LFCSP_WQ
Evaluation Board
for16-Lead LFCSP
Z = RoHS Compliant Part.
Rev. B | Page 25 of 28
Package Option
CP-8-2
CP-8-2
CP-8-2
Ordering Quantity
250
5,000
1,500
RD-8-1
RD-8-1
RD-8-1
1
2,500
1,000
CP-16-20
CP-16-20
CP-16-20
250
5,000
1,500
Branding
H1F
H1F
H1F
ADA4817-1/ADA4817-2
Data Sheet
NOTES
Rev. B | Page 26 of 28
Data Sheet
ADA4817-1/ADA4817-2
NOTES
Rev. B | Page 27 of 28
ADA4817-1/ADA4817-2
Data Sheet
NOTES
©2008–2013 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D07756-0-5/13(B)
Rev. B | Page 28 of 28