PDF Data Sheet Rev. 0

High Speed, High Voltage,
1 A Output Drive Amplifier
ADA4870
Data Sheet
FUNCTIONAL BLOCK DIAGRAM
Ideal for driving high capacitive or low resistive loads
Wide supply range: 10 V to 40 V
High output current drive: 1 A
Wide output voltage swing: 37 V swing with 40 V supply
High slew rate: 2500 V/µs
High bandwidth: 52 MHz large signal, 70 MHz small signal
Low noise: 2.1 nV/√Hz
Quiescent current: 32.5 mA
Power down: 0.75 mA
Short-circuit protection and flag
Current limit: 1.2 A
Thermal protection
VCC 1
20
ADA4870
VCC
19
VCC
SD 3
18
VCC
ON 4
17
OUT
NC 5
16
OUT
OUT
TFL 2
INP 6
15
INN 7
14
OUT
OUT 8
13
VEE
NC 9
12
VEE
VEE 10
11
VEE
12125-001
FEATURES
Figure 1.
APPLICATIONS
Envelope tracking
Power FET driver
Ultrasound
Piezo drivers
PIN diode drivers
Waveform generation
Automated test equipment (ATE)
CCD panel drivers
Composite amplifiers
GENERAL DESCRIPTION
The ADA4870 is available in a power SOIC package (PSOP_3),
featuring an exposed thermal slug that provides high thermal
conductivity, enabling efficient heat transfer for improved performance and reliability in demanding applications. The ADA4870
operates over the industrial temperature range (−40°C to +85°C).
Rev. 0
10
2,000
5
1,000
0
15
SLEW RATE
0
–1,000
–5
–2,000
–10
–3,000
–15
–20
–4,000
TIME (45ns/DIV)
VOUT (V)
3,000
VOUT
12125-057
The ADA4870 is ideal for driving high voltage power FETs,
piezo transducers, PIN diodes, CCD panels, and a variety of
other demanding applications that require high speed from
high supply voltage at high output current.
20
4,000
SLEW RATE (V/µs)
The ADA4870 is a unity gain stable, high speed current
feedback amplifier capable of delivering 1 A of output current
and 2500 V/μs slew rate from a 40 V supply. Manufactured
using the Analog Devices, Inc., proprietary high voltage extra
fast complementary bipolar (XFCB) process, the innovative
architecture of the ADA4870 enables high output power, high
speed signal processing solutions in applications that require
driving a low impedance load.
Figure 2. Slew Rate, VS = ±20 V, VOUT = 30 V p-p, AV = +2,
RF = 1.5 kΩ, CL = 300 pF, RS = 5 Ω
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rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
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Tel: 781.329.4700
©2014 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
ADA4870
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Shutdown (SD) ........................................................................... 19
Applications ....................................................................................... 1
Feedback Resistor Selection ...................................................... 19
Functional Block Diagram .............................................................. 1
Capacitive Load Driving ........................................................... 19
General Description ......................................................................... 1
Heat and Thermal Management .............................................. 20
Revision History ............................................................................... 2
Power Dissipation....................................................................... 20
Specifications..................................................................................... 3
Safe Operating Area ................................................................... 21
±20 V Supply ................................................................................. 3
Printed Circuit Board (PCB) .................................................... 22
±5 V Supply ................................................................................... 4
Thermal Modeling ..................................................................... 22
Absolute Maximum Ratings............................................................ 6
Heat Sink Selection .................................................................... 22
Maximum Power Dissipation ..................................................... 6
Power Supplies and Decoupling ............................................... 22
ESD Caution .................................................................................. 6
Composite Amplifier ................................................................. 23
Pin Configuration and Function Descriptions ............................. 7
Outline Dimensions ....................................................................... 24
Typical Performance Characteristics ............................................. 8
Ordering Guide .......................................................................... 24
Applications Information .............................................................. 19
ON, Initial Power-Up, and Short-Circuit ................................ 19
Thermal Protection .................................................................... 19
REVISION HISTORY
5/14—Revision 0: Initial Version
Rev. 0 | Page 2 of 24
Data Sheet
ADA4870
SPECIFICATIONS
±20 V SUPPLY
TCASE = 25°C, AV = −5, RF = 1.21 kΩ, RG = 243 Ω, CL = 300 pF, RS = 5 Ω, unless otherwise noted.
Table 1.
Parameter
DYNAMIC PERFORMANCE
−3 dB Bandwidth
Slew Rate (Peak)
Settling Time to 0.1%
NOISE/DISTORTION PERFORMANCE
Harmonic Distortion, HD2/HD3
Input Voltage Noise Density
Input Current Noise Density
INP
INN
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift
Input Bias Current
Noninverting Input
Inverting Input
Input Bias Current Drift, Inverting Input
Open-Loop Transresistance
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
Input Common-Mode Voltage Range (VICM)
Common-Mode Rejection Ratio
SD PIN (SHUTDOWN)
Input Voltages
Input Bias Current
ON PIN (RESET AND SHORT-CIRCUIT
PROTECTION)
Input Voltages
Input Bias Current
OUTPUT CHARACTERISTICS
Output Voltage Range
Output Current Drive
Short-Circuit Protection Current Limit
Test Conditions/Comments
Min
Typ
Max
Unit
VOUT = 2 V p-p
VOUT = 2 V p-p, AV = +2
VOUT = 20 V p-p
VOUT = 30 V step, AV = +2
VOUT = 10 V step
60
70
52
2500
82
MHz
MHz
MHz
V/µs
ns
f = 30 MHz, VOUT = 20 V p-p, AV = −10
f = 1 MHz, VOUT = 20 V p-p, AV = −10
f = 0.1 MHz, VOUT = 20 V p-p, AV = −10
f = 1 MHz, VOUT = 20 V p-p, RL = 25 Ω, AV = −10
f = 0.1 MHz, VOUT = 20 V p-p, RL = 25 Ω, AV = −10
f = 100 kHz
f = 100 kHz
−40/−39
−91/−74
−95/−96
−70/−77
−79/−99
2.1
dBc
dBc
dBc
dBc
dBc
nV/√Hz
4.2
47
pA/√Hz
pA/√Hz
−15
INP
INP
VICM = ±2 V, ±18 V
58
High (enabled)
Low (power-down)
Enabled (SD = VEE + 5 V)
Power down SD = VEE)
VEE + 1.1
VEE
High (power-down)
Low (enabled)
Enabled (ON = VEE)
Power down (ON = VEE + 5 V)
VEE + 1.8
VEE
RG = 1.2 kΩ, RL = open
RG = 1.2 kΩ, RL = 50 Ω
ON = floating
Rev. 0 | Page 3 of 24
−1
4
+10
mV
µV/°C
9
−12
24
2.5
23
−25
µA
µA
nA/°C
MΩ
2
0.75
±18
60
MΩ
pF
V
dB
VEE + 5
VEE + 0.9
V
V
µA
µA
VEE + 5
VEE + 1.3
−75
100
V
V
µA
µA
±18.6
±18
1
1.2
V
V
A
A
110
−50
ADA4870
Parameter
POWER SUPPLY
Operating Range
Quiescent Current
Data Sheet
Test Conditions/Comments
Min
Typ
10
SD = VEE + 5 V, ON = VEE
SD = VEE, ON = not applicable
SD = VEE + 5 V, ON = VEE + 5 V
Positive Power Supply Rejection Ratio
Negative Power Supply Rejection Ratio
67
62
32.5
0.75
5.1
69
64
Max
Unit
40
33
1
5.8
V
mA
mA
mA
dB
dB
Max
Unit
±5 V SUPPLY
TCASE = 25°C, AV = −5, RF = 1.21 kΩ, RG = 243 Ω, CL = 300 pF, RS = 5 Ω, unless otherwise noted.
Table 2.
Parameter
DYNAMIC PERFORMANCE
−3 dB Bandwidth
Settling Time to 0.1%
NOISE/DISTORTION PERFORMANCE
Harmonic Distortion, HD2/HD3
Input Voltage Noise Density
Input Current Noise Density
INP
INN
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift
Input Bias Current
Noninverting Input
Inverting Input
Input Bias Current Drift, Inverting Input
Open-Loop Transresistance
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
Input Common-Mode Voltage Range (VICM)
Common-Mode Rejection Ratio
SD PIN (SHUTDOWN)
Input Voltages
Input Bias Current
ON PIN (RESET AND SHORT-CIRCUIT
PROTECTION)
Input Voltages
Input Bias Current
Test Conditions/Comments
Min
Typ
VOUT = 2 V p-p
VOUT = 2 V step
52
55
MHz
ns
f = 30 MHz, VOUT = 2 V p-p, AV = −10
f = 1 MHz, VOUT = 2 V p-p, AV = −10
f = 0.1 MHz, VOUT = 2 V p-p, AV = −10
f = 1 MHz, VOUT = 2 V p-p, RL = 25 Ω, AV = −10
f = 0.1 MHz, VOUT = 2 V p-p, RL = 25 Ω, AV = −10
f = 100 kHz
f = 100 kHz
−42/−38
−90/−88
−101/−107
−70/−66
−85/−86
2.1
dBc
dBc
dBc
dBc
dBc
nV/√Hz
4.2
47
pA/√Hz
pA/√Hz
−15
INP
INP
VICM = ±0.5 V, ±3.0 V
57
High (enabled)
Low (power-down)
Enabled (SD = VEE + 5 V)
Power down (SD = VEE)
VEE + 1.1
VEE
High (power-down)
Low (enabled)
Enabled (ON = VEE)
Power down (ON = VEE + 5 V)
VEE + 1.8
VEE
Rev. 0 | Page 4 of 24
−4
14
+5
mV
µV/°C
13
−5
10
1.9
23
−18
µA
µA
nA/°C
MΩ
2
0.75
±3.0
59
MΩ
pF
V
dB
VEE + 5
VEE + 0.9
V
V
µA
µA
VEE + 5
VEE + 1.3
V
V
µA
µA
110
−65
−75
100
Data Sheet
Parameter
OUTPUT CHARACTERISTICS
Output Voltage Range
Output Current Drive
Short-Circuit Protection Current Limit
POWER SUPPLY
Operating Range
Quiescent Current
ADA4870
Test Conditions/Comments
Min
RG = 1.2 kΩ, RL = open
Typ
±3.7
1
1.2
ON = floating
10
SD = VEE + 5 V, ON = VEE
SD = VEE, ON = not applicable
SD = VEE + 5 V, ON = VEE + 5 V
Positive Power Supply Rejection Ratio
Negative Power Supply Rejection Ratio
66
61
Rev. 0 | Page 5 of 24
Max
28
0.65
4.7
68
63
Unit
V
A
A
40
30
1
5.5
V
mA
mA
mA
dB
dB
ADA4870
Data Sheet
ABSOLUTE MAXIMUM RATINGS
MAXIMUM POWER DISSIPATION
Table 3.
Parameter
Supply Voltage
Power Dissipation
Common-Mode Input Voltage Range
Differential Input Voltage Range
Storage Temperature Range
Operating Temperature Range
Lead Temperature (Soldering, 10 sec)
Junction Temperature
Rating
42 V
See the Power Dissipation
section and the Safe
Operating Area section
VEE to VCC
±0.7 V
−65°C to +150°C
−40°C to +85°C
300°C
150°C
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
The maximum safe power dissipation in the package is limited by
the associated rise in junction temperature (TJ) on the die. At
approximately 150°C, which is the glass transition temperature,
the plastic changes its properties. Exceeding a junction temperature
of 150°C can result in changes in the silicon devices, potentially
causing failure. Table 4 shows the junction to case thermal
resistance (θJC) for the PSOP_3 package. For more detailed
information on power dissipation and thermal management,
see the Applications Information section.
Table 4. Thermal Resistance
Package Type
20-Lead PSOP_3
ESD CAUTION
Rev. 0 | Page 6 of 24
θJC
1.1
Unit
°C/W
Data Sheet
ADA4870
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
VCC 1
20 VCC
2
19 VCC
SD 3
18 VCC
17 OUT
ON 4
NC 5
ADA4870
16 OUT
INP 6
TOP VIEW
(Not to Scale)
15 OUT
INN 7
14 OUT
OUT 8
13 VEE
NC 9
12 VEE
VEE 10
11 VEE
NOTES
1. NC = NO CONNECT. DO NOT CONNECT TO THIS PIN.
2. CONNECT THE EXPOSED PAD TO A SOLID EXTERNAL
PLANE WITH LOW THERMAL RESISTANCE.
12125-102
TFL
Figure 3. Pin Configuration
Table 5. Pin Function Descriptions
Pin No.
1
2
3
4
5
6
7
8
9
10 to 13
14 to 17
18 to 20
Mnemonic
VCC
TFL
SD
ON
NC
INP
INN
OUT
NC
VEE
OUT
VCC
EPAD
Description
Positive Power Supply Input.
Thermal Monitor and Short-Circuit Flag (Referenced to VEE).
Shutdown (Active Low, Referenced to VEE).
Turn On/Enable (Active Low, Referenced to VEE).
No Connect. Do not connect to this pin.
Noninverting Input.
Inverting Input.
Output Connection for Feedback Resistor.
No Connect. Do not connect to this pin.
Negative Power Supply Input.
Output.
Positive Power Supply Input.
Exposed Thermal Pad. No internal electrical connection. Connect the exposed pad to a solid external plane
with low thermal resistance.
Rev. 0 | Page 7 of 24
ADA4870
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
TCASE = 25°C, unless otherwise noted.
12
12
–20°C
+25°C
+100°C
6
6
3
3
0
–3
–6
–6
10
100
1000
FREQUENCY (MHz)
–18
Figure 4. Small Signal Frequency Response vs. Case Temperature, AV = −2,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
1
10
100
Figure 7. Large Signal Frequency Response vs. Case Temperature, AV = −2,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
21
21
–20°C
+25°C
+100°C
18
15
12
12
GAIN (dB)
9
6
3
0
1
3
VS = ±20V
VOUT = 20V p-p
RF = 1.21kΩ
AV = −5
CL = 300pF
RS = 5Ω
–3
–6
10
100
1000
FREQUENCY (MHz)
–9
12125-003
–9
9
6
0
VS = ±5V
VOUT = 2V p-p
RF = 1.21kΩ
AV = −5
CL = 300pF
RS = 5Ω
–6
–20°C
+25°C
+100°C
18
15
–3
1000
FREQUENCY (MHz)
Figure 5. Small Signal Frequency Response vs. Case Temperature, AV = −5,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
1
10
100
Figure 8. Large Signal Frequency Response vs. Case Temperature, AV = −5,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
27
27
–20°C
+25°C
+100°C
24
1000
FREQUENCY (MHz)
12125-018
1
–15
12125-002
–18
VS = ±20V
VOUT = 20V p-p
RF = 1.21kΩ
AV = −2
CL = 300pF
RS = 5Ω
–12
12125-017
VS = ±5V
VOUT = 2V p-p
RF = 1.21kΩ
AV = −2
CL = 300pF
RS = 5Ω
–15
–20°C
+25°C
+100°C
24
21
18
18
15
15
GAIN (dB)
21
12
9
6
12
9
6
VS = ±5V
VOUT = 2V p-p
RF = 1.21kΩ
AV = −10
CL = 300pF
RS = 5Ω
0
–3
1
VS = ±20V
VOUT = 20V p-p
RF = 1.21kΩ
AV = −10
CL = 300pF
RS = 5Ω
3
0
10
100
FREQUENCY (MHz)
1000
–3
12125-004
3
Figure 6. Small Signal Frequency Response vs. Case Temperature, AV = −10,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
1
10
100
FREQUENCY (MHz)
1000
12125-019
GAIN (dB)
0
–3
–9
–9
–12
GAIN (dB)
–20°C
+25°C
+100°C
9
GAIN (dB)
GAIN (dB)
9
Figure 9. Large Signal Frequency Response vs. Case Temperature, AV = −10,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
Rev. 0 | Page 8 of 24
Data Sheet
ADA4870
12
12
–20°C
+25°C
+100°C
6
6
3
3
0
–3
–6
–6
–18
1
–15
10
100
1000
FREQUENCY (MHz)
–18
12125-006
–15
VS = ±20V
VOUT = 20V p-p
RF = 1.5kΩ
AV = +2
CL = 300pF
RS = 5Ω
–12
1
10
100
1000
FREQUENCY (MHz)
Figure 10. Small Signal Frequency Response vs. Case Temperature, AV = +2,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.5 kΩ, CL = 300 pF, RS = 5 Ω
12125-021
VS = ±5V
VOUT = 2V p-p
RF = 1.5kΩ
AV = +2
CL = 300pF
RS = 5Ω
–12
Figure 13. Large Signal Frequency Response vs. Case Temperature, AV = +2,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.5 kΩ, CL = 300 pF, RS = 5 Ω
21
21
–20°C
+25°C
+100°C
18
–20°C
+25°C
+100°C
18
15
15
12
12
9
9
GAIN (dB)
6
3
0
6
3
0
–6
–9
–6
10
1
VS = ±20V
VOUT = 20V p-p
RF = 1.21kΩ
AV = +5
CL = 300pF
RS = 5Ω
–3
100
1000
FREQUENCY (MHz)
–9
12125-007
–3
1
10
100
1000
FREQUENCY (MHz)
Figure 11. Small Signal Frequency Response vs. Case Temperature, AV = +5,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
12125-022
VS = ±5V
VOUT = 2V p-p
RF = 1.21kΩ
AV = +5
CL = 300pF
RS = 5Ω
Figure 14. Large Signal Frequency Response vs. Case Temperature, AV = +5,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
27
27
–20°C
+25°C
+100°C
24
–20°C
+25°C
+100°C
24
21
18
18
17
15
GAIN (dB)
21
12
9
6
12
9
6
VS = ±5V
VOUT = 2V p-p
RF = 1.21kΩ
AV = +10
CL = 300pF
RS = 5Ω
0
–3
1
VS = ±20V
VOUT = 20V p-p
RF = 1.21kΩ
AV = +10
CL = 300pF
RS = 5Ω
3
0
10
100
FREQUENCY (MHz)
1000
–3
12125-008
3
Figure 12. Small Signal Frequency Response vs. Case Temperature, AV = +10,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
1
10
100
FREQUENCY (MHz)
1000
12125-023
GAIN (dB)
0
–3
–9
–9
GAIN (dB)
–20°C
+25°C
+100°C
9
GAIN (dB)
GAIN (dB)
9
Figure 15. Large Signal Frequency Response vs. Case Temperature, AV = +10,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
Rev. 0 | Page 9 of 24
Data Sheet
27
27
24
24
21
21
18
18
15
GAIN (dB)
12
9
6
0
10
100
1000
FREQUENCY (MHz)
–3
1
1000
Figure 19. Large Signal Frequency Response, AV = −10,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 1000 pF, RS = 5 Ω
21
21
–20°C
+25°C
+100°C
18
–20°C
+25°C
+100°C
18
15
12
12
9
9
GAIN (dB)
15
6
3
0
6
3
0
1
–6
10
100
1000
FREQUENCY (MHz)
–9
12125-009
–6
VS = ±20V
VOUT = 20V p-p
RF = 1.21kΩ
AV = –5
RL = 50Ω
–3
Figure 17. Small Signal Frequency Response vs. Case Temperature, AV = −5,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, RL = 50 Ω
100
1000
FREQUENCY (MHz)
Figure 20. Large Signal Frequency Response vs. Case Temperature, AV = −5,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, RL = 50 Ω
21
21
–20°C
+25°C
+100°C
18
10
1
12125-025
VS = ±5V
VOUT = 2V p-p
RF = 1.21kΩ
AV = −5
RL = 50Ω
–3
–20°C
+25°C
+100°C
18
15
12
12
9
9
GAIN (dB)
15
6
3
0
6
RF = 1.21kΩ
AV = –5
RF = 1.5kΩ
AV = +2
3
0
VS = ±20V
VOUT = 20V p-p
RF = 1.21kΩ
AV = −5
RL = 20Ω
–6
1
–3
–6
10
100
FREQUENCY (MHz)
1000
12125-024
–3
–9
100
FREQUENCY (MHz)
Figure 16. Small Signal Frequency Response, AV = −10,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 1000 pF, RS = 5 Ω
–9
10
12125-028
1
VS = ±20V
VOUT = 20V p-p
RF = 1.21kΩ
AV = –10
CL = 1000pF
RS = 5Ω
3
12125-012
0
–3
GAIN (dB)
9
6
VS = ±5V
VOUT = 2V p-p
RF = 1.21kΩ
AV = −10
CL = 1000pF
RS = 5Ω
3
GAIN (dB)
15
12
Figure 18. Large Signal Frequency Response vs. Case Temperature, AV = −5,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, RL = 20 Ω
Rev. 0 | Page 10 of 24
–9
1M
VS = ±20V
VOUT = 2V p-p
CL = 300pF
RS = 5Ω
10M
100M
FREQUENCY (Hz)
1G
12125-206
GAIN (dB)
ADA4870
Figure 21. Small Signal Frequency Response vs. Case Temperature,
VS = ±20 V, VOUT = 2 V p-p, CL = 300 pF, RS = 5 Ω
Data Sheet
ADA4870
15
2.0
–20°C
+25°C
+100°C
–20°C
+25°C
+100°C
1.5
10
1.0
5
VOUT (V)
VOUT (V)
0.5
0
0
–0.5
–5
–1.0
–10
TIME (25ns/DIV)
–15
VS = ±20V
RF = 1.21kΩ
AV = –2
CL = 300pF
RS = 5Ω
TIME (25ns/DIV)
Figure 22. Small Signal Pulse Response vs. Case Temperature, AV = −2,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
Figure 25. Large Signal Pulse Response vs. Case Temperature, AV = −2,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
2.0
15
–20°C
+25°C
+100°C
–20°C
+25°C
+100°C
1.5
12125-045
–2.0
VS = ±5V
RF = 1.21kΩ
AV = –2
CL = 300pF
RS = 5Ω
12125-030
–1.5
10
1.0
5
VOUT (V)
VOUT (V)
0.5
0
0
–0.5
–5
–1.0
–10
TIME (25ns/DIV)
Figure 23. Small Signal Pulse Response vs. Case Temperature, AV = −5,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
–15
VS = ±20V
RF = 1.21kΩ
AV = –5
CL = 300pF
RS = 5Ω
12125-046
–2.0
VS = ±5V
RF = 1.21kΩ
AV = –5
CL = 300pF
RS = 5Ω
12125-031
–1.5
TIME (25ns/DIV)
Figure 26. Large Signal Pulse Response vs. Case Temperature, AV = −5,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
15
2.0
–20°C
+25°C
+100°C
–20°C
+25°C
+100°C
1.5
10
1.0
5
VOUT (V)
VOUT (V)
0.5
0
0
–0.5
–5
–2.0
VS = ±5V
RF = 1.21kΩ
AV = –10
CL = 300pF
RS = 5Ω
TIME (25ns/DIV)
–10
12125-032
–1.5
Figure 24. Small Signal Pulse Response vs. Case Temperature, AV = −10,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
–15
VS = ±20V
RF = 1.21kΩ
AV = –10
CL = 300pF
RS = 5Ω
TIME (25ns/DIV)
12125-047
–1.0
Figure 27. Large Signal Pulse Response vs. Case Temperature, AV = −10,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
Rev. 0 | Page 11 of 24
ADA4870
Data Sheet
2.0
15
–20°C
+25°C
+100°C
1.5
–20°C
+25°C
+100°C
10
1.0
5
VOUT (V)
VOUT (V)
0.5
0
0
–0.5
–5
–1.0
–10
TIME (25ns/DIV)
Figure 28. Small Signal Pulse Response vs. Case Temperature, AV = +2,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.5 kΩ, CL = 300 pF, RS = 5 Ω
–15
VS = ±20V
RF = 1.5kΩ
AV = +2
CL = 300pF
RS = 5Ω
12125-049
–2.0
VS = ±5V
RF = 1.5kΩ
AV = +2
CL = 300pF
RS = 5Ω
12125-034
–1.5
TIME (25ns/DIV)
Figure 31. Large Signal Pulse Response vs. Case Temperature, AV = +2,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.5 kΩ, CL = 300 pF, RS = 5 Ω
2.0
15
–20°C
+25°C
+100°C
–20°C
+25°C
+100°C
1.5
10
1.0
5
VOUT (V)
VOUT (V)
0.5
0
0
–0.5
–5
–1.0
–10
TIME (25ns/DIV)
–15
VS = ±20V
RF = 1.21kΩ
AV = +5
CL = 300pF
RS = 5Ω
12125-050
–2.0
VS = ±5V
RF = 1.21kΩ
AV = +5
CL = 300pF
RS = 5Ω
12125-035
–1.5
TIME (25ns/DIV)
Figure 29. Small Signal Pulse Response vs. Case Temperature, AV = +5,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
Figure 32. Large Signal Pulse Response vs. Case Temperature, AV = +5,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
2.0
15
–20°C
+25°C
+100°C
1.5
–20°C
+25°C
+100°C
10
1.0
5
VOUT (V)
VOUT (V)
0.5
0
0
–0.5
–5
–2.0
VS = ±5V
RF = 1.21kΩ
AV = +10
CL = 300pF
RS = 5Ω
TIME (25ns/DIV)
–10
12125-036
–1.5
–15
VS = ±20V
RF = 1.21kΩ
AV = +10
CL = 300pF
RS = 5Ω
TIME (25ns/DIV)
Figure 30. Small Signal Pulse Response vs. Case Temperature, AV = +10,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
12125-051
–1.0
Figure 33. Large Signal Pulse Response vs. Case Temperature, AV = +10,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 300 pF, RS = 5 Ω
Rev. 0 | Page 12 of 24
Data Sheet
ADA4870
15
2.0
1.5
10
1.0
5
VOUT (V)
VOUT (V)
0.5
0
0
–0.5
–2.0
VS = ±5V
RF = 1.5kΩ
AV = +2
CL = 1000pF
RS = 5Ω
TIME (40ns/DIV)
–10
12125-079
–1.5
VS = ±20V
RF = 1.5kΩ
AV = +2
CL = 1000pF
RS = 5Ω
–15
TIME (40ns/DIV)
Figure 34. Small Signal Pulse Response, AV = +2,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.5 kΩ, CL = 1000 pF, RS = 5 Ω
12125-083
–5
–1.0
Figure 37. Large Signal Pulse Response, AV = +2,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.5 kΩ, CL = 1000 pF, RS = 5 Ω
2.0
15
1.5
10
1.0
5
VOUT (V)
VOUT (V)
0.5
0
0
–0.5
–2.0
VS = ±5V
RF = 1.21kΩ
AV = –10
CL = 1000pF
RS = 5Ω
TIME (40ns/DIV)
–10
12125-081
–1.5
–15
VS = ±20V
RF = 1.21kΩ
AV = –10
CL = 1000pF
RS = 5Ω
TIME (40ns/DIV)
Figure 35. Small Signal Pulse Response, AV = −10,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 1000 pF, RS = 5 Ω
12125-085
–5
–1.0
Figure 38. Large Signal Pulse Response, AV = −10,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 1000 pF, RS = 5 Ω
2.0
15
1.5
10
1.0
5
VOUT (V)
0
0
–0.5
–1.5
–2.0
VS = ±5V
RF = 1.5kΩ
AV = +2
CL = 1µF
RS = 5Ω
TIME (25µs/DIV)
–10
VS = ±20V
RF = 1.5kΩ
AV = +2
CL = 1µF
RS = 5Ω
–15
TIME (25µs/DIV)
Figure 36. Small Signal Pulse Response, AV = +2,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.5 kΩ, CL = 1 μF, RS = 5 Ω
Figure 39. Large Signal Pulse Response, AV = +2,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.5 kΩ, CL = 1 μF, RS = 5 Ω
Rev. 0 | Page 13 of 24
12125-084
–5
–1.0
12125-080
VOUT (V)
0.5
ADA4870
Data Sheet
2.0
15
1.5
10
1.0
5
VOUT (V)
VOUT (V)
0.5
0
0
–0.5
–5
–1.0
VS = ±20V
RF = 1.21kΩ
AV = –10
CL = 1µF
RS = 5Ω
–10
TIME (25µs/DIV)
–15
12125-086
–2.0
VS = ±5V
RF = 1.21kΩ
AV = –10
CL = 1µF
RS = 5Ω
12125-082
–1.5
TIME (25µs/DIV)
Figure 40. Small Signal Pulse Response, AV = −10,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, CL = 1 μF, RS = 5 Ω
Figure 43. Large Signal Pulse Response, AV = −10,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, CL = 1μF, RS = 5 Ω
15
2.0
–20°C
+25°C
+100°C
–20°C
+25°C
+100°C
1.5
10
1.0
5
VOUT (V)
VOUT (V)
0.5
0
0
–0.5
–5
–1.0
Figure 41. Small Signal Pulse Response vs. Case Temperature, AV = −5,
VS = ±5 V, VOUT = 2 V p-p, RF = 1.21 kΩ, RL = 50 Ω
–15
TIME (25ns/DIV)
Figure 44. Large Signal Pulse Response vs. Case Temperature, AV = −5,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, RL = 50 Ω
15
OPEN-LOOP TRANSIMPEDANCE (dB)
–20°C
+25°C
+100°C
10
VOUT (V)
5
0
–10
–15
TIME (25ns/DIV)
12125-052
–5
12125-053
TIME (25ns/DIV)
140
200
120
150
PHASE
100
100
50
80
TRANSIMPEDANCE
60
0
40
–50
20
–100
0
–150
–20
1k
10k
100k
1M
10M
100M
–200
1G
FREQUENCY (Hz)
Figure 42. Large Signal Pulse Response vs. Case Temperature, AV = −5,
VS = ±20 V, VOUT = 20 V p-p, RF = 1.21 kΩ, RL = 20 Ω
Rev. 0 | Page 14 of 24
Figure 45. Open-Loop Transimpedance and Phase vs. Frequency
PHASE (Degrees)
–2.0
VS = ±20V
RF = 1.21kΩ
AV = –5
RL = 20Ω
VS = ±20V
RF = 1.21kΩ
AV = –5
RL = 50Ω
–10
12125-207
VS = ±5V
RF = 1.21kΩ
AV = –5
RL = 50Ω
12125-037
–1.5
Data Sheet
ADA4870
–40
–50
–60
–70
–80
–90
–100
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0.01
0.1
1
12125-060
–110
–120
0.01
10
FREQUENCY (MHz)
–60
CL = 300pF, RS = 5Ω
CL = 300pF, RS = 5Ω
RL = 25Ω
RL = 25Ω
–80
–90
–100
10
15
20
Figure 47. Harmonic Distortion vs. VOUT, VS = ±20 V, Frequency = 100 kHz,
RF = 1.21 kΩ, AV = −10
–100
HD2,
HD3,
HD2,
HD3,
HD2,
HD3,
HD2,
HD3,
0
5
10
15
–30
CL = 300pF, RS = 5Ω
CL = 300pF, RS = 5Ω
RL = 25Ω
RL = 25Ω
–50
–60
–40
–50
–60
HD2,
HD3,
HD2,
HD3,
10
VOUT (V p-p)
15
20
–70
12125-088
–70
5
20
Figure 50. Harmonic Distortion vs. VOUT, VS = ±20 V, Frequency = 1 MHz,
RF = 1.21 kΩ, AV = −10
–40
0
CL = 300pF, RS = 5Ω
CL = 300pF, RS = 5Ω
RL = 25Ω
RL = 25Ω
VOUT (V p-p)
HARMONIC DISTORTION (dBc)
HARMONIC DISTORTION (dBc)
–90
–120
12125-062
5
0
VOUT (V p-p)
–30
–80
–110
–110
–120
–70
12125-063
–70
10
Figure 49. Harmonic Distortion vs. Frequency, RL = 25 Ω,
RF = 1.21 kΩ, AV = −10
HARMONIC DISTORTION (dBc)
HARMONIC DISTORTION (dBc)
HD2,
HD3,
HD2,
HD3,
1
FREQUENCY (MHz)
Figure 46. Harmonic Distortion vs. Frequency, CL = 300 pF, RS = 5 Ω,
RF = 1.21 kΩ, AV = −10
–60
0.1
Figure 48. Harmonic Distortion vs. VOUT, VS = ±20 V, Frequency = 10 MHz,
RF = 1.21 kΩ, AV = −10
0
5
10
VOUT (V p-p)
CL = 300pF, RS = 5Ω
CL = 300pF, RS = 5Ω
RL = 25Ω
RL = 25Ω
15
20
12125-089
–30
HD2 2V p-p, VS = ±5V
HD3 2V p-p, VS = ±5V
HD2 20V p-p, VS = ±20V
HD3 20V p-p, VS = ±20V
–20
HARMONIC DISTORTION (dBc)
–20
HARMONIC DISTORTION (dBc)
–10
HD2 2V p-p, VS = ±5V
HD3 2V p-p, VS = ±5V
HD2 20V p-p, VS = ±20V
HD3 20V p-p, VS = ±20V
12125-061
–10
Figure 51. Harmonic Distortion vs. VOUT, VS = ±20 V, Frequency = 30 MHz,
RF = 1.21 kΩ, AV = −10
Rev. 0 | Page 15 of 24
ADA4870
Data Sheet
15
3,000
15
10
2,000
10
0
0
–10
–2,000
–10
–15
–3,000
–15
–2,000
–3,000
–20
TIME (45ns/DIV)
TIME (45ns/DIV)
VOUT
VIN
6
3.5
5
3.0
4
2.5
3
10
2
5
1
0
0
–5
–1
–10
–2
–15
–3
–20
–4
2.0
1.5
+100°C
+25°C
–20°C
VOUT – VEE
1.0
0.5
0
–0.5
–1.0
–1.5
VOUT – VCC
–2.0
–5
–30
–6
–3.0
12125-059
–25
–20°C
+25°C
+100°C
–2.5
TIME (150ns/DIV)
–3.5
10
100
1k
RLOAD (Ω)
Figure 53. Output Overdrive Recovery, VS = ± 20 V, AV = +5, RL = 50 Ω
Figure 56. Output Headroom vs. RLOAD Over Case Temperature, VS = ±20 V
10000
100
VS = ±20V
RF = 1.21kΩ
AV = +1
ON
OUTPUT IMPEDANCE (Ω)
10
1
1
10
100
1000
FREQUENCY (MHz)
12125-069
0.1
0.01
0.1
VS = ±20V
RF = 1.21kΩ
AV = +1
SD
Figure 54. Enabled Closed-Loop Output Impedance vs. Frequency
1000
100
10
1
0.1
1
10
100
1000
FREQUENCY (MHz)
Figure 57. Disabled Closed-Loop Output Impedance vs. Frequency
Rev. 0 | Page 16 of 24
12125-087
VOUT (V)
15
OUTPUT HEADROOM (V)
20
Figure 55. Large Signal Instantaneous Slew Rate, AV = +2,
VS = ±20 V, RF = 1.5 kΩ, RL = 25 Ω
VIN (V)
VS = ±20V
AV = +5
RL = 50Ω
–20
–4,000
Figure 52. Large Signal Instantaneous Slew Rate, AV = +2,
VS = ±20 V, RF = 1.5 kΩ, CL = 300 pF, RS = 5 Ω
25
0
–5
–5
30
SLEW RATE
–1,000
–1,000
–4,000
5
1,000
VOUT (V)
0
12125-057
SLEW RATE
VOUT (V)
5
1,000
OUTPUT IMPEDANCE (Ω)
SLEW RATE (V/µs)
2,000
VOUT
12125-072
3,000
20
4,000
SLEW RATE (V/µs)
VOUT
12125-058
20
4,000
Data Sheet
–10
–20
–30
–30
PSR (dB)
–20
–40
–40
–50
–50
–60
–60
–70
–70
–80
100
1k
100k
10k
1M
10M
100M
FREQUENCY (Hz)
–80
100
1k
10k
100k
1M
10M
100M
FREQUENCY (Hz)
Figure 61. Power Supply Rejection (PSR) vs. Frequency, VS = ±20 V
Figure 58. Common-Mode Rejection vs. Frequency
1000
INPUT CURRENT NOISE (pA/√Hz)
1
10
1
100
1k
10k
100k
1M
FREQUENCY (Hz)
10M
INN
10
INP
1
12125-209
10
100
1
10
100
1k
10k
100k
1M
10M
FREQUENCY (Hz)
12125-208
100
INPUT VOLTAGE NOISE (nV/√Hz)
+PSR
–PSR
–10
12125-064
CMR (dB)
0
VS = ±20V
VS = ±5V
12125-065
0
ADA4870
Figure 62. Input Current Noise vs. Frequency
Figure 59. Input Voltage Noise vs. Frequency
50
15
VS = ±10V
40
10
30
VS = ±5V
20
VOS (mV)
0
VOUT
10
VS = ±20V
0
–10
–5
–10
–20
–30
SD
–15
TIME (1µs/DIV)
–50
–20
–16
–12
–8
–4
0
4
8
12
16
VICM (V)
Figure 63. Input Common-Mode Voltage Range
Figure 60. Turn-On/Turn-Off Time, VS = ±10 V
Rev. 0 | Page 17 of 24
20
12125-073
–40
12125-070
VOLTAGE (V)
5
ADA4870
Data Sheet
1
3500
0
3000
VS = ±5V
VS = ±20V
NUMBER OF AMPLIFIERS
OFFSET VOLTAGE (mV)
VS = ±20V
–1
–2
–3
–4
2500
2000
1500
1000
VS = ±5V
25
45
65
85
TEMPERATURE (°C)
0
–10
14
1.2
10
20
VS = ±20V
0.8
15
VS = ±5V
0.6
Iq DISABLED (mA)
1.0
0
0
–14
85
TEMPERATURE (°C)
Figure 65. Quiescent Supply Current (Iq) vs. Temperature, VS = ±5 V, VS = ±20 V
(Enabled/Disabled via SD)
40
20
ENABLED
0
GAIN (dB)
–20
–40
DISABLED PIN = 10dBm
–60
–80
DISABLED PIN = 0dBm
–100
1k
10k
100k
1M
10M
FREQUENCY (Hz)
100M
1G
12125-068
–120
–140
6
8
10
Figure 66. Forward Isolation vs. Frequency for 0 dBm and 10 dBm Input Levels
(Disabled via SD or ON)
Rev. 0 | Page 18 of 24
INP, VS = ±5V
INN, VS = ±5V
–6
–10
65
4
–2
0.2
45
2
2
5
25
0
INP, VS = ±20V
0.4
0
–2
6
10
12125-076
Iq ENABLED (mA)
1.4
VS = ±5V
25
–4
Figure 67. Input Offset Voltage Distribution, VS = ±5 V,
VS = ±20 V
INPUT BIAS CURRENT (µA)
VS = ±20V
30
–6
VS (mV)
Figure 64. Input Offset Voltage vs. Temperature, VS = ±5 V,
VS = ±20 V
35
–8
INN, VS = ±20V
0
25
45
TEMPERATURE (°C)
65
85
12125-074
0
12125-075
–6
12125-077
500
–5
Figure 68. Input Bias Current vs. Temperature, VS = ±5 V, VS = ±20 V
Data Sheet
ADA4870
APPLICATIONS INFORMATION
ON, INITIAL POWER-UP, AND SHORT-CIRCUIT
Table 6. Recommended RF Values
After initial power-up, the ON pin must be pulled low to ensure
that the amplifier is turned on. Subsequently, floating the ON
pin enables the short-circuit protection feature while the
amplifier remains on. While ON is held low, the short-circuit
protection feature is disabled.
Closed-Loop
Gain (V/V)
+1
−1
+2
−2
+5
+10
Pulling the ON pin high disables the amplifier and causes the
supply current to drop to about 5 mA, as if a short-circuit
condition had been detected.
The impedance at the ON pin is ~20 kΩ. Lay out the PCB trace
leading to ON to avoid noise coupling into it and triggering a
false event. A 1 nF capacitor between ON and VEE is recommended
to help shunt noise away from ON.
THERMAL PROTECTION
In addition to short-circuit protection, the ADA4870 is also
protected against excessive die temperatures.
During normal operation, the TFL pin outputs a dc voltage
(referenced to VEE) ranging from 1.5 V to 1.9 V that is relative to
die temperature. The voltage on TFL changes at approximately
−3 mV/°C and can be used to indicate approximate increases in
die temperature. When excessive die temperatures are detected,
the amplifier switches to an off state, dropping the supply current to
approximately 5 mA, and TFL continues to report a voltage
relative to die temperature. When the die temperature returns
to an acceptable level, the amplifier automatically resumes
normal operation.
RG (Ω)
Open
1210
1500
604
301
133
CL (pF)
300
300
300
300
300
300
RS (Ω)
5
5
5
5
5
5
CAPACITIVE LOAD DRIVING
When driving a capacitive load (CL), the amplifier output resistance
and the load capacitance form a pole in the transfer function of
the amplifier. This additional pole reduces phase margin at
higher frequencies and, if left uncompensated, can result in
excessive peaking and instability. Placing a small series resistor (RS)
between the amplifier output and CL (as shown in Figure 69)
allows the ADA4870 to drive capacitive loads beyond 1 μF.
Figure 70 shows the series resistor value vs. capacitive load for a
maximum of 1 dB peaking in the circuit of Figure 69. For large
capacitive loads, RS values of less than 0.3 Ω are not
recommended.
Figure 71 shows the small signal bandwidth (SSBW) vs. CL with
corresponding RS values from Figure 70.
VIN
50Ω
RS
1.5kΩ
CL
1.5kΩ
12125-203
When a short-circuit condition is detected, the amplifier is
disabled, the supply current drops to about 5 mA, and the TFL
pin outputs a dc voltage of ~300 mV. To turn the amplifier back
on after a short-circuit event, follow the sequence for initial
power-up.
RF (Ω)
2000
1210
1500
1210
1210
1210
Figure 69. Circuit for Capacitive Load Drive
8
7
6
SHUTDOWN (SD)
5
RS (Ω)
The ADA4870 is equipped with a power saving shutdown feature.
Pulling SD low places the amplifier in a shutdown state, reducing
quiescent current to approximately 750 µA. When turning the
amplifier back on from the shutdown state, pull the SD pin high
and then pull the ON pin low. Following this sequence ensures
power-on. Afterwards, the ON pin can be floated to enable
short-circuit protection.
4
3
2
0
10p
Pull SD high or low; do not leave SD floating.
100p
1n
10n
CL (F)
100n
1µ
12125-204
1
Figure 70. RS vs. CL for Maximum 1 dB Peaking for Circuit from Figure 69
FEEDBACK RESISTOR SELECTION
The feedback resistor value has a direct impact on the stability
and closed-loop bandwidth of current feedback amplifiers.
Table 6 provides a guideline for the selection of feedback
resistors for some common gain configurations.
Rev. 0 | Page 19 of 24
ADA4870
Data Sheet
The total power dissipation in the amplifier is the sum of the
power dissipated in the output stage plus the quiescent power.
The average power for an amplifier processing sine signals is
computed by Equation 1. Equation 2 can be used to compute the
peak power of a sine wave and can be used to compute the
continuous power dissipation of dc output voltages where VPEAK is
the dc load voltage. These equations assume symmetrical supplies
and a load referred to midsupply.
9
6
0
–3
–6
CL = 330pF, RS = 6.8Ω
CL = 1nF, RS = 4Ω
–9
 2 V CC V PEAK
PAVG , SINE = (V S × I q ) +  ×
π
RL

CL = 3.3nF, RS = 2.5Ω
CL = 10nF, RS = 1.4Ω
–15
0.1
CL = 33nF, RS = 0.7Ω
CL = 100nF, RS = 0.3Ω




(1)
CL = 1µF, RS = 0.3Ω
1
10
100
FREQUENCY (MHz)
12125-205
–12
  V PEAK 2
–
  2R
L
 
V
PPEAK = (VS × I q ) + (VS – VPEAK ) ×  PEAK
 RL
Figure 71. Small Signal Bandwidth for Various CL and RS Values from Figure 70
HEAT AND THERMAL MANAGEMENT
High output current amplifiers like the ADA4870 generate heat,
instantaneous or continuous, depending on the signal being
processed. Properly applied thermal management techniques
move heat away from the ADA4870 die and help to maintain
acceptable junction temperatures (TJ). A highly conductive
thermal path from the slug of the PSOP_3 package to the
ambient air is required to obtain the best performance at the
lowest TJ.
POWER DISSIPATION
The first step in identifying a thermal solution is to compute the
power generated in the amplifier during normal operation. The
schematic in Figure 72 shows a simplified output stage of the
ADA4870. The most significant heat is generated by the output
stage push-pull pair, particularly when driving heavy loads.



(2)
where
VS is the total supply voltage (VCC – VEE).
Iq is the amplifier quiescent current.
A graphical representation of the PAVG, SINE and PPEAK power
equations is shown in Figure 73. The power curves were generated
for the ADA4870 operating from ±20 V supplies and driving a
20 Ω load. The quiescent power intersects the vertical axis at
~1.3 W when VOUT is at 0 V or midsupply. The graphs stop at
the output swing limit of 18 V.
For dc analysis, peak power dissipation occurs at VOUT = VCC/2,
while the maximum average power for sine wave signals occurs
at VOUT = 2VCC/π.
7
PEAK (W)
6
VCC
POWER (W)
5
AVG, SINE (W)
4
3
VOUT
2
RL
12125-113
GND
VEE
1
Figure 72. Simplified Output Stage
0
0
5
10
VOUT (V)
15
20
12125-114
GAIN (dB)
3
Figure 73. Average Sine and Peak Power vs. VOUT, VS = ±20 V, RL = 20 Ω
Rev. 0 | Page 20 of 24
Data Sheet
ADA4870
SAFE OPERATING AREA
1.1
The safe operating area (SOA) is a curve of output current vs.
output stage collector-emitter voltage (VCE), under which the
amplifier can operate at a safe junction temperature (TJ). The
area under the curves of Figure 74 shows the operational
boundaries of the ADA4870 for the PCB of Figure 75 that
maintains a TJ ≤ 150°C. The SOA curves of Figure 74 are unique
to the conditions under which they were developed, such as
PCB, heat sink, and ambient temperature.
1.0
MAXIMUM TJ = 150°C
All testing was done in a still-air environment. Forced air
convection in any of the test cases effectively lowers θJA and
moves the corresponding curve toward the upper right,
expanding the SOA. For more information on the ADA4870
evaluation board, see the ADA4870 User Guide.
OUTPUT CURRENT (A)
0.8
0.7
0.6
0.5
0.4
0.3
25°C WITH VHS-45
25°C NO HEATSINK
85°C WITH VHS-95
85°C WITH VHS-45
85°C NO HEATSINK
0.2
0.1
0
0
2
4
6
8
10
12
14
16
18
OUTPUT STAGE VCE (V)
Figure 74. Safe Operating Area for Evaluation Board from Figure 75 at 25°C
and 85°C Ambient Temperature With and Without Heat Sink, No Air Flow
In Figure 74, the horizontal line at 1 A is the output current
drive of the ADA4870. The curved section maintains a fixed
power dissipation that results in a junction temperature (TJ) of
150°C or less. Note that the x-axis is the output stage VCE (VCC −
VOUT or VOUT – VEE) developed across the relevant output
transistor of Figure 72 and ends at a maximum VCE of 20 V.
2.45in (62mm)
COPPER
TOP/BOTTOM: 1.5oz
INNER LAYERS: 1oz
Figure 75. Details of the ADA4870 Evaluation Board
Rev. 0 | Page 21 of 24
12125-116
2.33in (59mm)
EXPOSED PAD LANDING VIAS
COUNT: 136
FILL: AE3030
DIAMETER: 12mil
PITCH: 35mil
6-LAYER HR370 PCB
WITH INTERNAL GROUND
AND POWER PLANES
20
12125-115
Two heat sinks (VHS-45 and VHS-95) were used in the evaluation.
Both were assembled to the PCB using CT40-5 thermal interface
material.
0.9
ADA4870
Data Sheet
PRINTED CIRCUIT BOARD (PCB)
HEAT SINK SELECTION
All current feedback amplifiers, including the ADA4870, can be
affected by stray capacitance. Paying careful attention during
PCB layout can reduce parasitic capacitance and improve
overall circuit performance. Minimize signal trace lengths by
placing feedback and gain setting resistors as close as possible to
the amplifier.
A heat sink increases the surface area to ambient temperature
(TA) and extends the power dissipation capability of the
ADA4870 and PCB combination. To maximize heat transfer
from the board to the heat sink, attach the heat sink to the PCB
using a high conductivity thermal interface material (TIM). The
heat sinks presented in the Safe Operating Area section and
Figure 74 are effective up to ~10 W in still air. If lower power
dissipation is anticipated and/or forced air convection is used, a
smaller heat sink may be appropriate. If the thermal resistance
of the chip (θJC), PCB (θCB), and TIM (θTIM) are known, use
Equation 3 to compute the thermal resistance (θHS) of the
required heat sink.
Additionally, for high output current amplifiers like the
ADA4870, lay out the PCB with heat dissipation in mind. A
good thermal design includes an exposed copper landing area
on the top side of the board on which to solder the thermal slug
of the PSOP3 package. The PCB should also provide an exposed
copper area on the bottom side to accommodate a heat sink.
Stitch the top and bottom layers together with an array of
plated-through thermal vias to facilitate efficient heat transfer
through the board. Thermal conductivity may be further
improved by using widely available via fill materials.
THERMAL MODELING
Computational fluid dynamics (CFD) tools like FloTherm® can
be used to create layers of materials that include PCB construction,
thermal vias, thermal interface materials, and heat sinks, and
can predict junction temperature and/or junction to ambient
thermal resistance (θJA) for a given set of conditions. Table 7
shows an example of how θJA is affected by the addition of an
aluminum heat sink and forced convection. Figure 76 shows an
image of the model used to establish the thermal results in Table 7.
 TJ –TA
 P
DISS

θ HS = 

 – (θ + θ + θ
JC
CB
TIM


(3)
)
POWER SUPPLIES AND DECOUPLING
The ADA4870 can operate from a single supply or dual supplies.
The total supply voltage (VCC − VEE) must be between 10 V and
40 V. Decouple each supply pin to ground using high quality,
low ESR, 0.1 μF capacitors. Place decoupling capacitors as close
to the supply pins as possible. Additionally, place 22 μF tantalum
capacitors from each supply to ground to provide good low
frequency decoupling and supply the needed current to support
large, fast slewing signals at the ADA4870 output.
TBOARD
TCASE
DIE
TLEADS
TJUNCTION
12125-091
CU SLUG
ADA4870
TPLASTIC
Figure 76. Thermal Model Stack-Up for Data in Table 7
(Heat Sink Not Shown)
Table 7. Effects of Heat Sink and Forced Convection on θJA
Heat Sink Dimensions, L × W × Total Height (mm)
61 × 58, Exposed Copper on Board, No Heat Sink
61 × 58, Exposed Copper on Board, No Heat Sink
61 × 58, Exposed Copper on Board, No Heat Sink
30 × 30 × 24
30 × 30 × 24
30 × 30 × 24
61 × 58 × 24
61 × 58 × 24
61 × 58 × 24
Heat Sink Base Thickness (mm)
Not applicable
Not applicable
Not applicable
3
3
3
3
3
3
Rev. 0 | Page 22 of 24
No. of Fins
Not applicable
Not applicable
Not applicable
10
10
10
10
10
10
Air Flow (m/sec)
0
1
2
0
1
2
0
1
2
θJA (°C/W)
15.95
12.27
10.95
11.36
4.90
3.86
5.74
3.59
3.18
Data Sheet
ADA4870
COMPOSITE AMPLIFIER
1.5
By placing the ADA4870 inside the feedback loop of the
ADA4637-1, the composite amplifier provides the high output
current of the ADA4870 while preserving the dc precision of
the ADA4637-1.
0
–0.5
RS
–1.5
VOUT
TIME (100ns/DIV)
CL
3.01kΩ
VS = ±15V
CL = 300pF
RS = 10Ω
12125-201
ADA4870
50Ω
50Ω
0.5
–1.0
ADA4637-1
VIN
1.0
VOUT (V)
When dc precision and high output current are required, the
ADA4870 can be combined with a precision amplifier such as
the ADA4637-1 to form a composite amplifier as shown in
Figure 77.
Figure 79. Composite Amplifier Small Signal Pulse Response
3.01kΩ
1kΩ
110Ω
6pF
AV = 10V/V
OUTPUT OFFSET <500µV
12125-090
15
10
Figure 77. Composite Amplifier
The small signal and large signal pulse response is shown in
Figure 79 and Figure 80, respectively.
CL = 300pF
RS = 10Ω
VOUT = 1V p-p
–10
–15
–20
RL = 50Ω
VOUT = 1V p-p
–25
–30
–35
0.1
1
10
100
FREQUENCY (MHz)
1000
12125-200
GAIN (dB)
CL = 300pF
RS = 10Ω
VOUT = 10V p-p
0
VS = ±15V
CL = 300pF
RS = 10Ω
TIME (100ns/DIV)
15
–5
–10
Figure 80. Composite Amplifier Large Signal Pulse Response
20
5
–5
–15
25
10
0
Figure 78. Composite Amplifier Frequency Response
Rev. 0 | Page 23 of 24
12125-202
The circuit can be tailored for different gains as desired.
Depending on the board parasitics, the 6 pF capacitor may need
to be empirically adjusted to optimize performance. Minimize
PCB stray capacitance as much as possible, particularly in the
feedback path.
5
VOUT (V)
Figure 78 shows the bandwidth of the composite amplifier at a
gain of 10. The offset voltage at the output is <500 μV.
ADA4870
Data Sheet
OUTLINE DIMENSIONS
1.10 MAX × 45°
10
PIN 1
13.00
9.00
1
6.20
5.80
14.20
BSC
11.00
BSC
11
20
BOTTOM VIEW
TOP VIEW
1.10 MAX
(2 PLACES)
SEATING
PLANE
SIDE VIEW
1.27
BSC
2.90 MAX
(2 PLACES)
DETAIL A
1.00
0.90
0.80
8°
0°
0.53
0.40
3.30
3.15
3.00
END VIEW
1.10
0.80
DETAIL A
3.60
3.35
3.10
0.10
0.05
0.00
0.30
0.20
0.10
0.32
0.23
COMPLIANT TO JEDEC STANDARDS MO-166-AA
12-21-2011-A
15.90
BSC
3.60
3.35
3.10
Figure 81. 20-Lead Power SOIC, Thermally Enhanced Package [PSOP_3]
(RR-20-1)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
ADA4870ARRZ
ADA4870ARRZ-RL
ADA4870ARR-EBZ
1
Temperature Range
−40°C to +85°C
−40°C to +85°C
Package Description
20-Lead PSOP_3
20-Lead PSOP_3
Evaluation Board
Z = RoHs Compliant Part.
©2014 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D12125-0-5/14(0)
Rev. 0 | Page 24 of 24
Package Option
RR-20-1
RR-20-1