INTERSIL EL2126

EL2126
®
Data Sheet
May 9, 2005
Ultra-Low Noise, Low Power, Wideband
Amplifier
The EL2126 is an ultra-low noise, wideband amplifier that
runs on half the supply current of competitive parts. It is
intended for use in systems such as ultrasound imaging
where a very small signal needs to be amplified by a large
amount without adding significant noise. Its low power
dissipation enables it to be packaged in the tiny SOT-23
package, which further helps systems where many input
channels create both space and power dissipation problems.
FN7046.2
Features
• Voltage noise of only 1.3nV/√Hz
• Current noise of only 1.2pA/√Hz
• 200µV offset voltage
• 100MHz -3dB BW for AV = 10
• Very low supply current - 4.7mA
• SOT-23 package
• ±2.5V to ±15V operation
The EL2126 is stable for gains of 10 and greater and uses
traditional voltage feedback. This allows the use of reactive
elements in the feedback loop, a common requirement for
many filter topologies. It operates from ±2.5V to ±15V
supplies and is available in the 5-pin SOT-23 and 8-pin SO
packages.
• Pb-Free available (RoHS compliant)
The EL2126 is fabricated in Elantec’s proprietary
complementary bipolar process, and is specified for
operation over the full -40°C to +85°C temperature range.
• Communication equipment
Applications
• Ultrasound input amplifiers
• Wideband instrumentation
• AGC & PLL active filters
• Wideband sensors
Pinouts
EL2126
(5-PIN SOT-23)
TOP VIEW
OUT 1
Ordering Information
PART NUMBER
5 VS+
VS- 2
+
-
IN+ 3
4 IN-
EL2126
(8-PIN SO)
TOP VIEW
8 NC
NC 1
IN- 2
IN+ 3
7 VS+
+
6 OUT
5 NC
VS- 4
1
PACKAGE
TAPE & REEL PKG. DWG. #
EL2126CW-T7
5-Pin SOT-23
7” (3K pcs)
MDP0038
EL2126CW-T7A
5-Pin SOT-23
7” (250 pcs)
MDP0038
EL2126CS
8-Pin SO
-
MDP0027
EL2126CS-T7
8-Pin SO
7”
MDP0027
EL2126CS-T13
8-Pin SO
13”
MDP0027
EL2126CSZ
(See Note)
8-Pin SO
(Pb-free)
-
MDP0027
EL2126CSZ-T7
(See Note)
8-Pin SO
(Pb-free)
7”
MDP0027
EL2126CSZ-T13
(See Note)
8-Pin SO
(Pb-free)
13”
MDP0027
NOTE: Intersil Pb-free products employ special Pb-free material sets;
molding compounds/die attach materials and 100% matte tin plate
termination finish, which are RoHS compliant and compatible with
both SnPb and Pb-free soldering operations. Intersil Pb-free products
are MSL classified at Pb-free peak reflow temperatures that meet or
exceed the Pb-free requirements of IPC/JEDEC J STD-020.
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-352-6832 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2004, 2005. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
EL2126
Absolute Maximum Ratings (TA = 25°C)
Operating Temperature . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-60°C to +150°C
Maximum Die Junction Temperature . . . . . . . . . . . . . . . . . . . +150°C
VS+ to VS- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33V
Continuous Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . 40mA
Any Input . . . . . . . . . . . . . . . . . . . . . . . . . . VS+ - 0.3V to VS- + 0.3V
Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Curves
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests
are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
Electrical Specifications
PARAMETER
VS+ = +5V, VS- = -5V, TA = 25°C, RF = 180Ω, RG = 20Ω, RL = 500Ω unless otherwise specified.
DESCRIPTION
CONDITIONS
MIN
TYP
MAX
UNIT
0.2
2
mV
3
mV
DC PERFORMANCE
VOS
Input Offset Voltage (SO8)
Input Offset Voltage (SOT23-5)
TCVOS
Offset Voltage Temperature
Coefficient
IB
Input Bias Current
IOS
Input Bias Current Offset
0.06
TCIB
Input Bias Current Temperature
Coefficient
0.013
µA/°C
CIN
Input Capacitance
2.2
pF
AVOL
Open Loop Gain
80
87
dB
PSRR
Power Supply Rejection Ratio
(Note 1)
80
100
dB
CMRR
Common Mode Rejection Ratio
75
106
dB
CMIR
Common Mode Input Range
VOUTH
Positive Output Voltage Swing
No load, RF = 1kΩ
VOUTL
Negative Output Voltage Swing
No load, RF = 1kΩ
VOUTH2
Positive Output Voltage Swing
RL = 100Ω
VOUTL2
Negative Output Voltage Swing
RL = 100Ω
IOUT
Output Short Circuit Current
(Note 2)
ISY
Supply Current
-10
VO = -2.5V to +2.5V
at CMIR
17
µV/°C
-7
µA
-4.6
3.8
3.8
3.8
-4
3.2
-3.9
V
V
V
-3.2
100
4.7
µA
V
3.45
-3.5
80
0.6
V
mA
5.5
mA
AC PERFORMANCE - RG = 20Ω, CL = 3pF
BW
-3dB Bandwidth, RL = 500Ω
100
MHz
BW ±0.1dB
±0.1dB Bandwidth, RL = 500Ω
17
MHz
BW ±1dB
±1dB Bandwidth, RL = 500Ω
80
MHz
Peaking
Peaking, RL = 500Ω
0.6
dB
SR
Slew Rate
VOUT = 2VPP, measured at 20% to 80%
110
V/µs
OS
Overshoot, 4Vpk-pk Output Square
Wave
Positive
2.8
%
Negative
-7
%
80
tS
Settling Time to 0.1% of ±1V Pulse
51
ns
VN
Voltage Noise Spectral Density
1.3
nV/√Hz
IN
Current Noise Spectral Density
1.2
pA/√Hz
2
EL2126
Electrical Specifications
PARAMETER
VS+ = +5V, VS- = -5V, TA = 25°C, RF = 180Ω, RG = 20Ω, RL = 500Ω unless otherwise specified. (Continued)
DESCRIPTION
CONDITIONS
MIN
TYP
MAX
UNIT
HD2
2nd Harmonic Distortion (Note 3)
-70
dBc
HD3
3rd Harmonic Distortion (Note 3)
-70
dBc
NOTES:
1. Measured by moving the supplies from ±4V to ±6V
2. Pulse test only and using a 10Ω load
3. Frequency = 1MHz, VOUT = 2Vpk-pk, into 500Ω and 5pF load
VS+ = +15V, VS- = -15V, TA = 25°C, RF = 180Ω, RG = 20Ω, RL = 500Ω unless otherwise specified.
Electrical Specifications
PARAMETER
DESCRIPTION
CONDITIONS
MIN
TYP
MAX
UNIT
0.5
3
mV
3
mV
DC PERFORMANCE
VOS
Input Offset Voltage (SO8)
Input Offset Voltage (SOT23-5)
TCVOS
Offset Voltage Temperature
Coefficient
IB
Input Bias Current
IOS
Input Bias Current Offset
0.12
TCIB
Input Bias Current Temperature
Coefficient
0.016
µA/°C
CIN
Input Capacitance
2.2
pF
AVOL
Open Loop Gain
80
90
dB
PSRR
Power Supply Rejection Ratio
(Note 1)
65
80
dB
CMRR
Common Mode Rejection Ratio
70
85
dB
CMIR
Common Mode Input Range
VOUTH
Positive Output Voltage Swing
No load, RF = 1kΩ
VOUTL
Negative Output Voltage Swing
No load, RF = 1kΩ
VOUTH2
Positive Output Voltage Swing
RL = 100Ω, RF = 1kΩ
VOUTL2
Negative Output Voltage Swing
RL = 100Ω, RF = 1kΩ
IOUT
Output Short Circuit Current
(Note 2)
ISY
Supply Current
-10
at CMIR
4.5
µV/°C
-7
µA
-14.6
13.6
13.8
13.7
-13.8
10.2
-13.7
V
V
V
-9.5
220
5
µA
V
11.2
-10.3
140
0.7
V
mA
6
mA
AC PERFORMANCE - RG = 20Ω, CL = 3pF
BW
-3dB Bandwidth, RL = 500Ω
135
MHz
BW ±0.1dB
±0.1dB Bandwidth, RL = 500Ω
26
MHz
BW ±1dB
±1dB Bandwidth, RL = 500Ω
60
MHz
Peaking
Peaking, RL = 500Ω
2.1
dB
SR
Slew Rate (±2.5V Square Wave,
Measured 25%-75%)
150
V/µS
OS
Overshoot, 4Vpk-pk Output Square
Wave
Positive
1.6
%
Negative
-4.4
%
130
TS
Settling Time to 0.1% of ±1V Pulse
48
ns
VN
Voltage Noise Spectral Density
1.4
nV/√Hz
3
EL2126
VS+ = +15V, VS- = -15V, TA = 25°C, RF = 180Ω, RG = 20Ω, RL = 500Ω unless otherwise specified. (Continued)
Electrical Specifications
PARAMETER
DESCRIPTION
CONDITIONS
MIN
TYP
MAX
UNIT
IN
Current Noise Spectral Density
1.1
pA/√Hz
HD2
2nd Harmonic Distortion (Note 3)
-72
dBc
HD3
3rd Harmonic Distortion (Note 3)
-73
dBc
NOTES:
1. Measured by moving the supplies from ±13.5V to ±16.5V
2. Pulse test only and using a 10Ω load
3. Frequency = 1MHz, VOUT = 2Vpk-pk, into 500Ω and 5pF load
4
EL2126
Typical Performance Curves
Non-Inverting Frequency Response for Various RF
Non-Inverting Frequency Response for Various RF
6
10
VS=±5V
AV=10
CL=5pF
RL=500Ω
RF=1kΩ
Normalized Gain (dB)
Normalized Gain (dB)
10
RF=500Ω
2
-2
RF=180Ω
-6
RF=100Ω
-10
1M
10M
6
VS=±15V
AV=10
CL=5pF
RL=500Ω
-2
RF=180Ω
RF=100Ω
-6
Frequency (Hz)
Inverting Frequency Response for Various RF
Inverting Frequency Response for Various RF
RF=500Ω
RF=1kΩ
Normalized Gain (dB)
Normalized Gain (dB)
VS=±5V
AV=-10
CL=5pF
RL=500Ω
RF=350Ω
RF=200Ω
-4
RF=100Ω
-8
-12
1M
10M
4
VS=±15V
AV=-10
CL=5pF
RL=500Ω
RF=500Ω
RF=350Ω
RF=200Ω
-4
RF=100Ω
-8
-12
1M
100M
RF=1kΩ
0
Frequency (Hz)
10M
100M
Frequency (Hz)
Non-Inverting Frequency Response for Various Gain
Non-Inverting Frequency Response for Various Gain
10
10
VS=±5V
RG=20Ω
RL=500Ω
CL=5pF
2
AV=10
AV=20
-2
AV=50
-6
-10
1M
10M
Frequency (Hz)
5
100M
Normalized Gain (dB)
Normalized Gain (dB)
100M
8
0
6
10M
Frequency (Hz)
8
4
RF=500Ω
2
-10
1M
100M
RF=1kΩ
6
VS=±15V
RG=20Ω
RL=500Ω
CL=5pF
AV=10
2
AV=20
-2
AV=50
-6
-10
1M
10M
Frequency (Hz)
100M
EL2126
Typical Performance Curves
(Continued)
Inverting Frequency Response for Various Gain
Inverting Frequency Response for Various RF
4
8
VS=±5V
CL=5pF
RG=35Ω
0
Normalized Gain (dB)
Normalized Gain (dB)
8
AV=-10
-4
AV=-50
AV=-20
-8
-12
1M
10M
4
VS=±15V
CL=5pF
RG=20Ω
0
AV=-10
-4
AV=-50
-12
1M
100M
10M
Frequency (Hz)
Non-Inverting Frequency Response for Various
Output Signal Levels
Non-Inverting Frequency Response for Various
Output Signal Levels
VS=±5V
CL=5pF
RL=500Ω
RF=180Ω
AV=10
VO=500mVPP
-4
VO=30mVPP
VO=5VPP
VO=2.5VPP
-8
Normalized Gain (dB)
Normalized Gain (dB)
10
0
VO=1VPP
-12
1M
10M
6
VS=±15V
CL=5pF
RL=500Ω
RF=180Ω
AV=10
VO=1VPP
-2
VO=10VPP
VO=5VPP
-6
-10
1M
100M
VO=2.5VPP
10M
100M
Frequency (Hz)
Inverting Frequency Response for Various Output
Signal Levels
Inverting Frequency Response for Various Output
Signal Levels
8
8
VS=±5V
CL=5pF
RL=500Ω
RF=350Ω
AV=10
VO=500mVPP
VO=1VPP
VO=30mVPP
0
VO=3.4VPP
-4
VO=2.5VPP
-8
-12
1M
10M
Frequency (Hz)
6
100M
Normalized Gain (dB)
Normalized Gain (dB)
VO=30mVPP
VO=500mVPP
2
Frequency (Hz)
4
100M
Frequency (Hz)
8
4
AV=-20
-8
4
VS=±15V
CL=5pF
RL=500Ω
RF=200Ω
AV=10
VO=500mVPP
VO=1VPP
VO=30mVPP
0
-4
-8
-12
1M
VO=3.4VPP
VOV=2.5V
O=2.5V
PPP
10M
Frequency (Hz)
100M
EL2126
Typical Performance Curves
(Continued)
Non-Inverting Frequency Response for Various CL
Non-Inverting Frequency Response for Various CL
10
VS=±5V
RF=150Ω
AV=10
RL=500Ω
6
CL=28pF
CL=11pF
2
Normalized Gain (dB)
Normalized Gain (dB)
10
CL=16pF
CL=5pF
-2
CL=1pF
-6
-10
1M
10M
VS=±15V
RF=180Ω
AV=10
RL=500Ω
6
CL=5pF
CL=1.2pF
-6
10M
100M
Frequency (Hz)
Inverting Frequency Response for Various CL
Inverting Frequency Response for Various CL
8
8
VS=±5V
RF=350Ω
RL=500Ω
AV=-10
CL=28pF
CL=16pF
Normalized Gain (dB)
Normalized Gain (dB)
CL=16pF
-2
Frequency (Hz)
4
CL=11pF
2
-10
1M
100M
CL=28pF
0
CL=11pF
-4
CL=5pF
CL=1.2pF
-8
-12
1M
10M
4
VS=±15V
RF=200Ω
RL=500Ω
AV=-10
0
CLC=11pF
L=11p
-4
CL=5pF
CL=1.2pF
-8
-12
1M
100M
CL=28pF
CL=16pF
Frequency (Hz)
10M
Frequency (Hz)
Open Loop Gain/Phase
Supply Current vs Supply Voltage
100
250
Phase
60
50
40
-50
20
-150
VS=±5V
0
100k
10k
1M
10M
Frequency (Hz)
7
100M
-250
1G
Supply Current (mA)
150
Open Loop Phase (°)
Open Loop Gain (dB)
Gain
80
0.6/div
0
0
1.5/div
Supply Voltage (V)
100M
EL2126
Typical Performance Curves
(Continued)
Bandwidth vs Vs
Peaking vs Vs
160
3.0
VS=±5V
RG=20Ω
RL=500Ω
CL=5pF
-3dB Bandwidth
120
AV=-10
AV=10
100
80
AV=-20
60
40
AV=-20
AV=50
0
0
2
4
6
8
10
12
14
2.0
AV=10
1.5
1.0
0.5
AV=-50
20
VS=±5V
RG=20Ω
RL=500Ω
CL=5pF
2.5
Peaking (dB)
140
AV=-10
0
16
0
2
4
6
8
12
10
14
16
±Supply Voltage (V)
±VS (V)
Small Signal Step Response
Large Signal Step Response
RF=180Ω VS=±5V
RG=20Ω VO=2VPP
20mV/div
0.5V/div
RF=180Ω
RG=20Ω
VS=±5V
VO=100mV
10ns/div
10ns/div
1MHz Harmonic Distortion vs Output Swing
1MHz Harmonic Distortion vs Output Swing
-30
VS=±5V
VO=2VP-P
RF=180Ω
AV=10
RL=500Ω
-50
-60
Harmonic Distortion (dBc)
Harmonic Distortion (dBc)
-40
2nd HD
-70
-80
3rd HD
-90
-100
VS=±5V
VO=2VP-P
RF=180Ω
AV=10
RL=500Ω
-40
-50
2nd HD
-60
-70
3rd HD
-80
-90
-100
0
1
2
3
4
5
VOUT (VP-P)
8
6
7
8
0
5
10
15
VOUT (VP-P)
20
25
EL2126
Typical Performance Curves
(Continued)
Total Harmonic Distortion vs Frequency
Noise vs Frequency
-20
10
VS=±5V
VO=2VP-P
IN (pA/√Hz), VN (nV/√Hz)
-30
THD (dBc)
-40
-50
-60
-70
IN, VS=±5V
VN, VS=±15V
VN, VS=±5V
-80
-90
1k
100k
10k
1M
10M
1
10
100M
IN, VS=±15V
10k
100k
100M
400M
Frequency (Hz)
Settling Time vs Accuracy
Group Delay vs Frequency
70
16
VS =
± 15
50
VS =
±5V
,V
VS =
20
±15
V, V
VS=±5V
RL=500Ω
12
-P
V, V
40
30
VO =
5V
P
Group Delay (ns)
VS =
±5V
,
60
Settling Time (ns)
1k
100
Frequency (Hz)
O =5V
P-P
O =2V
P-P
O =2V
P-P
AV=10
8
4
AV=-10
0
10
0
0.1
1.0
-4
1M
10.0
10M
Accuracy (%)
Frequency (Hz)
CMRR vs Frequency
PSRR vs Frequency
-10
110
VS=±5V
90
PSRR (dB)
CMRR (dB)
-30
-50
-70
-90
-110
10
PSRR-
70
50
PSRR+
30
100
1k
10k
100k
Frequency (Hz)
9
1M
10M
100M
10
10k
100k
1M
Frequency (Hz)
10M
200M
EL2126
(Continued)
Closed Loop Output Impedance vs Frequency
Bandwidth and Peaking vs Temperature
100
3.5
VS=±5V
VS=±5V
10
1
2.5
Bandwidth
80
2
60
1.5
1
40
Peaking
0.1
0.5
20
0.01
10k
1M
100k
100M
10M
0
0
-40
-0.5
40
0
Frequency (Hz)
80
120
160
Temperature
Slew Rate vs Swing
Supply Current vs Temperature
220
5.2
15VSR-
200
180
VS=±15V
5.1
160
15VSR+
IS (mA)
Slew Rate (V/µs)
3
100
Bandwidth (MHz)
Closed Loop Output Impedance (Ω)
120
140
120
5VSR-
100
5VSR+
5
VS=±5V
4.9
80
60
-1
1
3
5
7
9
11
13
4.8
-50
15
0
VOUT Swing (VPP)
50
100
150
100
150
Die Temperature (°C)
CMRR vs Temperature
Offset Voltage vs Temperature
1
120
VS=±5V
110
CMRR (dB)
VOS (mV)
0
VS=±15V
VS=±5V
100
-1
90
-2
-50
0
50
Die Temperature (°C)
10
100
150
80
-50
0
50
Die Temperature (°C)
Peaking (dB)
Typical Performance Curves
EL2126
Typical Performance Curves
(Continued)
Positive Output Swing vs Temperature
PSRR vs Temperature
110
4.05
106
VOUTH (V)
PSRR (dB)
4
VS=±5V
102
98
94
3.95
VS=±5V
3.9
90
VS=±15V
3.85
86
82
-50
0
50
100
3.8
-50
150
0
50
100
150
Die Temperature (°C)
Die Temperature (°C)
Positive Output Swing vs Temperature
Negative Output Swing vs Temperature
13.85
-3.9
-3.95
13.8
VOUTL (V)
VOUTH (V)
-4
VS=±15V
13.75
13.7
VS=±5V
-4.05
-4.1
-4.15
13.65
-4.2
13.6
-50
0
50
100
-4.25
-50
150
0
Die Temperature (°C)
50
100
150
100
150
Die Temperature (°C)
Negative Output Swing vs Temperature
Slew Rate vs Temperature
-13.76
102
Slew Rate (V/µs)
100
VOUTL (V)
-13.78
VS=±15V
-13.8
VS=±5V
98
96
94
92
90
-13.82
-50
0
50
Die Temperature (°C)
11
100
150
88
-50
0
50
Die Temperature (°C)
EL2126
Typical Performance Curves
(Continued)
Slew Rate vs Temperature
Positive Loaded Output Swing vs Temperature
155
3.52
3.5
VS=±15V
VOUTH2 (V)
SR (V/µs)
150
145
140
VS=±5V
3.48
3.46
135
-50
VO=2VPP
0
50
100
3.44
-50
150
0
Die Temperature (°C)
Positive Loaded Output Swing vs Temperature
150
-3.35
11.6
-3.4
VS=±15V
VOUTL2 (V)
11.4
SR (V/µs)
100
Negative Loaded Output Swing vs Temperature
11.8
11.2
11
-3.45
-3.5
VS=±5V
3.55
10.8
10.6
-50
0
50
100
-3.6
-50
150
0
Die Temperature (°C)
-9.6
1
Power Dissipation (W)
1.2
VS=±15V
-10
-10.2
150
781mW
0.8
SO
8
θJ
A =1
0.6
488mW
0.4
0.2
-10.4
60
°C
/
W
SOT
23θJ
5
A =25
6°C
/W
0
0
50
100
150
25
0
Die Temperature (°C)
50
1.8
1.6
1.4
1.2 1.136W
θJ
1
SO
8
10
°C
/W
A =1
0.8
0.6 543mW
0.4
0.2
SOT
23-5
θJ =
A 230
°C/W
0
0
25
50
75 85 100
Ambient Temperature (°C)
12
75 85 100
Ambient Temperature (°C)
Package Power Dissipation vs Ambient Temperature
JEDEC JESD51-7 High Effective Thermal Conductivity
Test Board
Power Dissipation (W)
-10.6
-50
100
Package Power Dissipation vs Ambient Temperature
JEDEC JESD51-3 Low Effective Thermal Conductivity
Test Board
-9.4
-9.8
50
Die Temperature (°C)
Negative Loaded Output Swing vs Temperature
VOUTL2 (V)
50
Die Temperature (°C)
125
150
125
150
EL2126
Pin Descriptions
EL2126CW
(5-PIN SOT-23)
EL2126CS
(8-PIN SO)
PIN NAME
PIN FUNCTION
1
6
VOUT
Output
EQUIVALENT CIRCUIT
VS+
VOUT
Circuit 1
2
4
VS-
Supply
3
3
VINA+
Input
VS+
VIN+
VIN-
VSCircuit 2
4
2
VINA-
Input
5
7
VS+
Supply
13
Reference Circuit 2
EL2126
Applications Information
Noise Calculations
Product Description
The EL2126 is an ultra-low noise, wideband monolithic
operational amplifier built on Elantec's proprietary high
speed complementary bipolar process. It features 1.3nV/√Hz
input voltage noise, 200µV typical offset voltage, and 73dB
THD. It is intended for use in systems such as ultrasound
imaging where very small signals are needed to be
amplified. The EL2126 also has excellent DC specifications:
200µV VOS, 22µA IB, 0.4µA I OS, and 106dB CMRR. These
specifications allow the EL2126 to be used in DC-sensitive
applications such as difference amplifiers.
The primary application for the EL2126 is to amplify very
small signals. To maintain the proper signal-to-noise ratio, it
is essential to minimize noise contribution from the amplifier.
Figure 2 below shows all the noise sources for all the
components around the amplifier.
VIN
R3
VR3
VN
+
-
I N+
VR1
I N-
R2
The EL2126 has a gain-bandwidth product of 650MHz at
±5V. For gains less than 20, higher-order poles in the
amplifier's transfer function contribute to even higher closedloop bandwidths. For example, the EL2126 has a -3dB
bandwidth of 100MHz at a gain of 10 and decreases to
33MHz at gain of 20. It is important to note that the extra
bandwidth at lower gain does not come at the expenses of
stability. Even though the EL2126 is designed for gain ≥ 10.
With external compensation, the device can also operate at
lower gain settings. The RC network shown in Figure 1
reduces the feedback gain at high frequency and thus
maintains the amplifier stability. R values must be less than
RF divided by 9 and 1 divided by 2πRC must be less than
200MHz.
FIGURE 2.
VN is the amplifier input voltage noise
IN+ is the amplifier positive input current noise
IN- is the amplifier negative input current noise
VRX is the thermal noise associated with each resistor:
V RX =
k is Boltzmann's constant = 1.380658 x 10-23
T is temperature in degrees Kelvin (273+ °C)
R
+
4kTRx
where:
RF
VOUT
VIN
FIGURE 1.
Choice of Feedback Resistor, RF
The feedback resistor forms a pole with the input
capacitance. As this pole becomes larger, phase margin is
reduced. This increases ringing in the time domain and
peaking in the frequency domain. Therefore, RF has some
maximum value which should not be exceeded for optimum
performance. If a large value of RF must be used, a small
capacitor in the few pF range in parallel with RF can help to
reduce this ringing and peaking at the expense of reducing
the bandwidth. Frequency response curves for various RF
values are shown in the typical performance curves section
of this data sheet.
V ON =
R1
VR2
Gain-Bandwidth Product
C
VON
The total noise due to the amplifier seen at the output of the
amplifier can be calculated by using the following equation
(Figure 3).
As the equation shows, to keep noise at a minimum, small
resistor values should be used. At higher amplifier gain
configuration where R2 is reduced, the noise due to IN-, R2,
and R1 decreases and the noise caused by IN+, VN, and R3
starts to dominate. Because noise is summed in a rootmean-squares method, noise sources smaller than 25% of
the largest noise source can be ignored. This can greatly
simplify the formula and make noise calculation much easier
to calculate.
Output Drive Capability
The EL2126 is designed to drive low impedance load. It can
easily drive 6VP-P signal into a 100Ω load. This high output
drive capability makes the EL2126 an ideal choice for RF, IF,
R 2
R 2
R  2
 R 1 2


2
2 
2 
2
2
BW ×  VN ×  1 + ------1- + IN- × R 1 + IN+ × R 3 ×  1 + ------1- + 4 × K × T × R 1 + 4 × K × T × R 2 ×  ------- + 4 × K × T × R 3 ×  1 + ------1- 
R
R
R
R 2 
 2




2
2
FIGURE 3.
14
EL2126
and video applications. Furthermore, the EL2126 is currentlimited at the output, allowing it to withstand momentary
short to ground. However, the power dissipation with outputshorted cannot exceed the power dissipation capability of
the package.
Driving Cables and Capacitive Loads
Although the EL2126 is designed to drive low impedance
load, capacitive loads will decreases the amplifier's phase
margin. As shown in the performance curves, capacitive load
can result in peaking, overshoot and possible oscillation. For
optimum AC performance, capacitive loads should be
reduced as much as possible or isolated with a series
resistor between 5Ω to 20Ω. When driving coaxial cables,
double termination is always recommended for reflectionfree performance. When properly terminated, the
capacitance of the coaxial cable will not add to the capacitive
load seen by the amplifier.
Power Supply Bypassing And Printed Circuit
Board Layout
As with any high frequency devices, good printed circuit
board layout is essential for optimum performance. Ground
plane construction is highly recommended. Lead lengths
should be kept as short as possible. The power supply pins
must be closely bypassed to reduce the risk of oscillation.
The combination of a 4.7µF tantalum capacitor in parallel
with 0.1µF ceramic capacitor has been proven to work well
when placed at each supply pin. For single supply operation,
where pin 4 (VS-) is connected to the ground plane, a single
4.7µF tantalum capacitor in parallel with a 0.1µF ceramic
capacitor across pins 7 (VS+) and pin 4 (VS-) will suffice.
For good AC performance, parasitic capacitance should be
kept to a minimum. Ground plane construction again should
be used. Small chip resistors are recommended to minimize
series inductance. Use of sockets should be avoided since
they add parasitic inductance and capacitance which will
result in additional peaking and overshoot.
Supply Voltage Range and Single Supply
Operation
The EL2126 has been designed to operate with supply
voltage range of ±2.5V to ±15V. With a single supply, the
EL2126 will operate from +5V to +30V. Pins 4 and 7 are the
power supply pins. The positive power supply is connected
to pin 7. When used in single supply mode, pin 4 is
connected to ground. When used in dual supply mode, the
negative power supply is connected to pin 4.
As the power supply voltage decreases from +30V to +5V, it
becomes necessary to pay special attention to the input
voltage range. The EL2126 has an input voltage range of
0.4V from the negative supply to 1.2V from the positive
supply. So, for example, on a single +5V supply, the EL2126
has an input voltage range which spans from 0.4V to 3.8V.
The output range of the EL2126 is also quite large, on a +5V
supply, it swings from 0.4V to 3.8V.
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
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