ETC EL2125CW-T13

Ultra-Low Noise, Low Power, Wideband Amplifier
®
Features
General Description
•
•
•
•
•
•
•
The EL2125C 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.
Voltage noise of only 0.83nV/√Hz
Current noise of only 2.4pA/√Hz
200µV offset voltage
175MHz -3dB BW for AV=10
Low supply current - 10mA
SOT-23 package available
±2.5V to ±15V operation
The EL2125C 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.
Applications
•
•
•
•
•
EL2125C
EL2125C
®
Ultrasound input amplifiers
Wideband instrumentation
Communication equipment
AGC & PLL active filters
Wideband sensors
The EL2125C is fabricated in Elantec’s proprietary complementary
bipolar process, and is specified for operation from -45°C to +85°C.
Ordering Information
Package
Tape &
Reel
Outline #
EL2125CW-T7
5-Pin SOT-23*
7”
MDP0038
EL2125CW-T13
5-Pin SOT-23*
13”
MDP0038
8-Pin SO
-
MDP0027
Part No
EL2125CS
EL2125CS-T7
8-Pin SO
7”
MDP0027
EL2125CS-T13
8-Pin SO
13”
MDP0027
Connection Diagrams
*EL2125CW symbol is .Fxxx where xxx represents date code
NC 1
OUT 1
5 VS+
VS- 2
IN- 2
IN+ 3
+
8 NC
+
7 VS+
6 OUT
-
IN+ 3
4 IN-
5 NC
EL2125CS
(8-Pin SO)
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-ELANTEC or 408-945-1323 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Elantec ® is a registered trademark of Elantec Semiconductor, Inc.
Copyright © Intersil Americas Inc. 2002. All Rights Reserved
November 14, 2002
EL2125CW
(5-Pin SOT-23)
VS- 4
EL2125C
EL2125C
Ultra-Low Noise, Low Power, Wideband Amplifier
Absolute Maximum Ratings (T
A
VS+ to VSContinuous Output Current
Any Input
Power Dissipation
= 25°C)
33V
40mA
VS- - 0.3V to VS+ + 0.3V
See Curves
Operating Temperature
Storage Temperature
Maximum Die Junction Temperature
-45°C to +85°C
-60°C to +150°C
+150°C
Important Note:
All parameters having Min/Max specifications are guaranteed. Typ 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 Characteristics
VS = ±5V, TA = 25°C, RF = 180Ω, RG = 20Ω, RL = 500Ω unless otherwise specified.
Parameter
Description
Conditions
Min
Typ
Max
Unit
0.2
2
mV
DC Performance
VOS
Input Offset Voltage (SO8)
Input Offset Voltage (SOT23-5)
3
TCVOS
Offset Voltage Temperature Coefficient
IB
Input Bias Current
IOS
Input Bias Current Offset
0.4
TCIB
Input Bias Current Temperature
Coefficient
0.09
CIN
Input Capacitance
AVOL
Open Loop Gain
1.8
-30
[1]
PSRR
Power Supply Rejection Ratio
Common Mode Rejection Ratio
CMIR
Common Mode Input Range
VOUTH
Output Voltage Swing High
No load, RF = 1kΩ
at CMIR
-22
VOUTL
Output Voltage Swing Low
No load, RF = 1kΩ
Output Voltage Swing High
RL = 100Ω
VOUTL2
Output Voltage Swing Low
RL = 100Ω
IOUT
Output Short Circuit Current
pF
dB
80
97
dB
80
106
IS
Supply Current
3.5
3.65
-3.7
V
V
-3
100
10.1
V
V
3.3
-3.5
80
dB
3.8
-3.87
3
[2]
µA
µA/°C
87
-4.6
VOUTH2
µA
2
2.2
80
CMRR
mV
µV/°C
V
mA
11
mA
AC Performance - RG = 20Ω, CL = 5pF
BW
-3dB Bandwidth
175
BW ±0.1dB
±0.1dB Bandwidth
34
MHz
MHz
BW ±1dB
±1dB Bandwidth
150
MHz
Peaking
Peaking
SR
Slew Rate
VOUT = 2VPP, measured at 20% to 80%
OS
Overshoot, 4Vpk-pk Output Square
Wave
0.4
dB
185
V/µs
Positive
0.6
%
Negative
2.7
%
42
ns
150
tS
Settling Time to 0.1% of ±1V Pulse
VN
Voltage Noise Spectral Density
0.83
nV/√Hz
IN
Current Noise Spectral Density
2.4
pA/√Hz
HD2
2nd Harmonic Distortion
[3]
-74
dBc
HD3
3rd Harmonic Distortion
[4]
-91
dBc
1. Measured by moving the supplies from ±4V to ±6V
2. Pulse test only
3. Frequency = 1MHz, VOUT = 2Vpk-pk, into 500Ω and 5pF load
2
Ultra-Low Noise, Low Power, Wideband Amplifier
Electrical Characteristics
VS = ±15V, TA = 25°C, RF = 180Ω, RG = 20Ω, RL = 500Ω unless otherwise specified.
Parameter
Description
Conditions
Min
Typ
Max
Unit
0.6
3
mV
DC Performance
VOS
Input Offset Voltage (SO8)
Input Offset Voltage (SOT23-5)
3
TCVOS
Offset Voltage Temperature Coefficient
IB
Input Bias Current
IOS
Input Bias Current Offset
0.4
TCIB
Input Bias Current Temperature
Coefficient
0.08
CIN
Input Capacitance
AVOL
Open Loop Gain
4.9
-30
[1]
Power Supply Rejection Ratio
CMRR
Common Mode Rejection Ratio
CMIR
Common Mode Input Range
VOUTH
Output Voltage Swing High
No load, RF = 1kΩ
VOUTL
Output Voltage Swing Low
No load, RF = 1kΩ
VOUTH2
Output Voltage Swing High
RL = 100Ω
VOUTL2
Output Voltage Swing Low
IOUT
Output Short Circuit Current
IS
Supply Current
at CMIR
-24
µA
µA/°C
pF
87
dB
80
97
dB
75
105
-14.6
13.35
RL = 100Ω
13.5
-13
V
V
-9.8
250
10.8
V
V
11.6
-10.4
120
dB
13.8
-13.6
11
[2]
µA
2
2.2
80
PSRR
mV
µV/°C
V
mA
12
mA
AC Performance - RG = 20Ω, CL = 5pF
BW
-3dB Bandwidth
220
MHz
BW ±0.1dB
±0.1dB Bandwidth
23
MHz
BW ±1dB
±1dB Bandwidth
63
MHz
Peaking
Peaking
2.5
dB
SR
Slew Rate
225
V/µs
OS
Overshoot, 4Vpk-pk Output Square
Wave
0.6
%
tS
Settling Time to 0.1% of ±1V Pulse
VN
Voltage Noise Spectral Density
VOUT = 2VPP, measured at 20% to 80%
180
38
ns
0.95
nV/√Hz
IN
Current Noise Spectral Density
2.1
pA/√Hz
HD2
2nd Harmonic Distortion
[3]
-73
dBc
HD3
3rd Harmonic Distortion
[4]
-96
dBc
1. Measured by moving the supplies from ±13.5V to ±16.5V
2. Pulse test only
3. Frequency = 1MHz, VOUT = 2Vpk-pk, into 500Ω and 5pF load
3
EL2125C
EL2125C
Ultra-Low Noise, Low Power, Wideband Amplifier
Typical Performance Curves
Non-Inverting Frequency Response for Various RF
Non-Inverting Frequency Response for Various RF
5
VS=±5V
AV=10
RL=500Ω
CL=5pF
RF=1kΩ
RF=499Ω
Normalized Gain (dB)
Normalized Gain (dB)
5
0
RF=180Ω
VS=±15V
AV=10
RL=500Ω
CL=5pF
RF=1kΩ
-5
1M
RF=499Ω
RF=180Ω
RF=100Ω
-5
1M
100M 200M
10M
10M
Frequency (Hz)
100M
300M
Frequency (Hz)
Inverting Frequency Response for Various RF
Inverting Frequency Response for Various RF
6
6
2
RF=1kΩ
-2
RF=350Ω
RF=499Ω
RF=200Ω
-6
RF=97.6Ω
-10
-14
1M
RF=1kΩ
2
Normalized Gain (dB)
Normalized Gain (dB)
RF=700Ω
0
RF=100Ω
VS=±5V
AV=-10
RL=560Ω
CL=5pF
-2
RF=200Ω
-6
-10
10M
100M
-14
1M
300M
RF=97.6Ω
VS=±15V
AV=-10
RL=500Ω
CL=5pF
10M
100M
300M
Frequency (Hz)
Non-Inverting Frequency Response vs Gain
Non-Inverting Frequency Response for Various Gain
5
5
Normalized Gain (dB)
VS=±5V
RL=500Ω
CL=5pF
RG=20Ω
AV=10
0
AV=50
-5
1M
RF=499Ω
RF=350Ω
Frequency (Hz)
Normalized Gain (dB)
EL2125C
EL2125C
AV=20
10M
VS=±15V
RL=500Ω
CL=5pF
RF=700Ω
AV=10
0
AV=20
AV=50
-5
1M
100M 200M
10M
Frequency (Hz)
Frequency (Hz)
4
100M 200M
Ultra-Low Noise, Low Power, Wideband Amplifier
Typical Performance Curves
Inverting Frequency Response vs Gain
Inverting Frequency Response vs Gain
6
6
AV=-10
AV=-10
Normalized Gain (dB)
Normalized Gain (dB)
2
-2
AV=-50
-6
-10
-14
1M
VS=±5V
RL=500Ω
CL=5pF
RG=35Ω
0
100M
-14
1M
300M
Frequency (Hz)
100M
300M
Inverting Frequency Response for Various Output Signal
Levels
5
6
VS=±5V
AV=10
RF=180Ω
RL= 500Ω
CL=5pF
3mVPP
30mVPP
500mVPP
0
4VPP
2VPP
0
3.3VPP
2.5VPP
1VPP
-5
1M
10M
-14
1M
100M 200M
VS=±5V
AV=-10
RF=350Ω
RL= 500Ω
CL=5pF
100M
300M
Frequency (Hz)
Non-Inverting Frequency Response for Various CL
Non-Inverting Frequency Response for Various CL
5
5
VS=±5V
AV=10
RF=180Ω
RL=500Ω
VS=±5V
AV=10
RF=700Ω
RL=500Ω
Normalized Gain (dB)
CL=28.5pF
CL=16pF
1
-1
CL=5pF
CL=17pF
CL=11pF
0
CL=5pF
CL=1.2pF
CL=1pF
-3
-5
1M
1VPP
10M
Frequency (Hz)
3
500mVPP
250mVPP
Normalized Gain (dB)
Normalized Gain (dB)
10M
Frequency (Hz)
Non-Inverting Frequency Response for Various Output
Signal Levels
Normalized Gain (dB)
AV=-20
VS=±15V
RL=500Ω
CL=5pF
RG=50Ω
AV=-20
10M
AV=-50
10M
-5
1M
100M 200M
Frequency (Hz)
10M
Frequency (Hz)
5
100M 200M
EL2125C
EL2125C
Ultra-Low Noise, Low Power, Wideband Amplifier
Typical Performance Curves
Inverting Frequency Response for Various CL
Inverting Frequency Response for Various CL
6
6
CL=29.4pF
CL=29.4pF
2
Normalized Gain (dB)
Normalized Gain (dB)
CL=16.4pF
0
CL=11.4pF
CL=5.1pF
-14
1M
CL=1.2pF
VS=±5V
AV=10
RF=350Ω
RL=500Ω
CL=16.4pF
-2
CL=11.4pF
CL=5.1pF
-6
CL=1.2pF
-10
10M
100M
-14
1M
300M
VS=±15V
AV=10
RF=500Ω
RL=500Ω
10M
100M
300M
12
15
Frequency (Hz)
Frequency (Hz)
Open Loop Gain and Phase
Supply Current vs Supply Voltage
100
250
12
Gain
150
Supply Current (mA)
Phase
9.6
60
50
40
-50
20
-150
2.4
-250
400M
0
Phase (°)
Open Loop Gain (dB)
80
7.2
4.8
VS=±5V
0
10k
100k
10M
1M
100M
0
6
3
Frequency (Hz)
9
Supply Voltage (±V)
3dB Bandwidth vs Supply Voltage
Peaking vs Supply Voltage
250
3
AV=10
200
2.5
AV=-10
150
Peaking (dB)
Bandwidth (MHz)
EL2125C
EL2125C
100
AV=-20
AV=20
AV=50
2
AV=10
AV=-10
1.5
1
AV=-50
50
0.5
AV=-20
0
2
4
6
8
10
12
14
AV=-50
AV=20
AV=50
0
16
2
VS (±V)
4
6
8
10
VS (±V)
6
12
14
16
Ultra-Low Noise, Low Power, Wideband Amplifier
Typical Performance Curves
Small Signal Step Response
Small Signal Step Response
VS=±15V
RL=500Ω
RF=180Ω
AV=10
CL=5pF
20mV/div
20mV/div
VS=±5V
RL=500Ω
RF=180Ω
AV=10
CL=5pF
VINx2
VO
VINx2
VO
10ns/div
10ns/div
Large-Signal Step Response
Large-Signal Step Response
VS=±15V
RL=500Ω
RF=180Ω
AV=10
CL=5pF
Output Voltage (0.5V/div)
Output Voltage (0.5V/div)
VS=±5V
RL=500Ω
RF=180Ω
AV=10
CL=5pF
Time (20ns/div)
Time (20ns/div)
1MHz Harmonic Distortion vs Output Swing
1MHz Harmonic Distortion vs Output Swing
-40
-30
VS=±5V
RF=180Ω
AV=10
RL=500Ω
Distortion (dBc)
-60
VS=±15V
RF=180Ω
AV=10
RL=500Ω
-40
-50
Distortion (dBc)
-50
2nd HD
-70
-80
3rd HD
-90
2nd HD
-60
-70
-80
3rd HD
-90
-100
-100
-110
-110
0
1
2
3
4
5
6
7
0
VOUT (VPP)
5
10
15
VOUT (VPP)
7
20
25
EL2125C
EL2125C
Ultra-Low Noise, Low Power, Wideband Amplifier
Typical Performance Curves
Voltage and Current Noise vs Frequency
Voltage Noise (nV/√Hz), Current Noise (pA/√Hz)
Total Harmonic Distortion vs Frequency
-30
VS=±5V
VO=2VPP
AV=10
RF=180Ω
RL=500Ω
-40
THD (dBc)
-50
-60
-70
-80
-90
1k
10k
100k
1M
10M
100M
100
10
IN, VS=±5V
IN, VS=±15V
VN, VS=±15V
1
VN, VS=±5V
0.1
10
100
Frequency (Hz)
1k
10k
100k
Frequency (Hz)
Settling Time vs Accuracy
Group Delay
14
60
VS=±15V
VS=±15V
VO=5VPP
10
VS=±5V
VO=5VPP
40
Group Delay (ns)
Settling Time (ns)
50
30
VS=±5V
VO=2VPP
20
VS=±15V
VO=2VPP
AV=20
6
2
AV=10
-2
10
-6
0
0.1
1
1
10
10
100
400
Frequency (MHz)
Accuracy (%)
CMRR
PSRR
-10
110
-30
90
-50
70
PSRR (dB)
PSRRCMRR (dB)
EL2125C
EL2125C
-70
-99
-110
10
PSRR+
50
30
100
1k
10k
100k
1M
10M
10
10K
100M
Frequency (Hz)
100K
1M
10M
Frequency (Hz)
8
100M
600M
Ultra-Low Noise, Low Power, Wideband Amplifier
Typical Performance Curves
Closed Loop Output Impedance vs Frequency
Bandwidth vs Temperature
100
200
10
160
3.5
1
0.1
120
2
Peaking
1.5
80
1
40
0.01
0.5
0.001
10k
100k
1M
10M
0
-40
100M
0
40
80
120
0
160
Temperature (°C)
Frequency (Hz)
Slew Rate vs Swing
Supply Current vs Temperature
350
13
300
15VSR-
12
250
IS (mA)
Slew Rate (V/µs)
2.5
5VSR200
VS=±15V
11
10
150
5VSR+
VS=±5V
15VSR+
100
0
5
10
15
9
-50
20
0
VOUT Swing (VPP)
50
100
150
100
150
Die Temperature (°C)
Offset Voltage vs Temperature
Input Bias Current vs Temperature
0
-10
VS=±5V
-15
-1
IB+ (µA)
VOS (mV)
VS=±15V
-20
-2
-25
-3
-50
0
50
100
-30
-50
150
Die Temperature (°C)
0
50
Die Temperature (°C)
9
Peaking (dB)
-3dB Bandwidth (MHz)
ROUT (Ω)
3
Bandwidth
EL2125C
EL2125C
Ultra-Low Noise, Low Power, Wideband Amplifier
Typical Performance Curves
CMRR vs Temperature
PSRR vs Temperature
120
110
VS=±15V
VS=±5V
100
PSRR (dB)
CMRR (dB)
100
80
VS=±5V
60
-50
0
50
VS=±15V
90
100
80
-50
150
0
Die Temperature (°C)
100
150
100
150
Positive Output Swing vs Temperature
240
3.9
VO=2VPP
VS=±15V
3.8
VOUTH (V)
220
SR (V/µs)
50
Die Temperature (°C)
Slew Rate vs Temperature
200
3.7
VS=±5V
VS=±5V
180
3.6
160
-50
0
50
100
3.5
-50
150
0
Die Temperature (°C)
50
Die Temperature (°C)
Positive Output Swing vs Temperature
Negative Output Swing vs Temperature
13.6
-9.75
-9.8
VS=±15V
VS=±5V
VOUTL (V)
VOUTH (V)
EL2125C
EL2125C
13.5
-9.85
-9.9
13.4
-50
0
50
100
-9.95
-50
150
Die Temperature (°C)
0
50
Die Temperature (°C)
10
100
Ultra-Low Noise, Low Power, Wideband Amplifier
Typical Performance Curves
Negative Output Swing vs Temperature
Loaded Negative Output Swing vs Temperature
-13.4
-3.42
-3.44
-13.5
VOUTL2 (V)
VOUTL (V)
VS=±15V
-3.46
VS=±5V
-3.48
-13.6
-3.5
-13.7
-50
0
50
100
-3.52
-50
150
0
Die Temperature (°C)
50
100
150
Die Temperature (°C)
Negative Output Swing vs Temperature
Loaded Positive Output Swing vs Temperature
-9.6
3.35
-9.8
VOUTH2 (V)
VOUTL2 (V)
-10
VS=±15V
-10.2
VS=±5V
3.3
-10.4
-10.6
-10.8
-50
0
50
100
3.25
-50
150
0
Die Temperature (°C)
Loaded Positive Output Swing vs Temperature
150
1.2
1
11.8
Power Dissipation (W)
VS=±15V
VOUTH2 (V)
100
Package Power Dissipation vs Ambient Temperature
JEDEC JESD51-3 Low Effective Thermal Conductivity Test Board
12
11.6
11.4
11.2
11
-50
50
Die Temperature (°C)
781mW
0.8
θJ
0.6
488mW
0.4
0.2
A =1
SO
8
60°
C /W
SOT
23-5
θJA =
256
°C/W
0
0
50
100
150
0
Die Temperature (°C)
25
50
75 85
100
Ambient Temperature (°C)
11
125
150
EL2125C
EL2125C
Ultra-Low Noise, Low Power, Wideband Amplifier
Typical Performance Curves
Package Power Dissipation vs Ambient Temperature
JEDEC JESD51-7 High Effective Thermal Conductivity Test Board
1.8
1.6
1.4
Power Dissipation (W)
EL2125C
EL2125C
1.136W
1.2
1
θJ
A =1
0.8
543mW
0.6
0.4
0.2
SO
8
10
°C/
W
SOT2
3-5
θJA =2
30°C
/W
0
0
25
50
75 85
100
125
150
Ambient Temperature (°C)
12
Ultra-Low Noise, Low Power, Wideband Amplifier
Pin Descriptions
EL2125CW
(5-Pin SOT-23)
EL2125CS
(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
Reference Circuit 2
13
EL2125C
EL2125C
EL2125C
EL2125C
Ultra-Low Noise, Low Power, Wideband Amplifier
Applications Information
Product Description
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 the in
typical performance curves section of this data sheet.
The EL2125C is an ultra-low noise, wideband monolithic operational amplifier built on Elantec's proprietary
high speed complementary bipolar process. It features
0.83nV/√Hz input voltage noise, 200µV 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 EL2125C also has excellent DC
specifications: 200µ V VOS, 22µA IB, 0.4µA IOS, and
106dB CMRR. These specifications allow the EL2125C
to be used in DC-sensitive applications such as difference amplifiers.
Noise Calculations
The primary application for the EL2125C is to amplify
very small signals. To maintain the proper signal-tonoise 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.
Gain-Bandwidth Product
The EL2125C has a gain-bandwidth product of 800MHz
at ±5V. For gains greater than 20, its closed-loop -3dB
bandwidth is approximately equal to the gain-bandwidth
product divided by the small signal gain of the circuit.
For gains less than 20, higher-order poles in the amplifier's transfer function contribute to even higher closedloop bandwidths. For example, the EL2125C has a -3dB
bandwidth of 175MHz at a gain of 10 and decreases to
40MHz 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 EL2125C 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 400MHz.
R3
VIN
+
-
VON
VR1
R1
IN -
VR2
R2
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
R
C
VN
IN+
RF
+
VR3
VRX is the thermal noise associated with each resistor:
VOUT
VIN
V RX =
4kTRx
where:
Figure 1.
- k is Boltzmann's constant = 1.380658 x 10-23
- T is temperature in degrees Kelvin (273+ °C)
Choice of Feedback Resistor, RF
The feedback resistor forms a pole with the input capacitance. As this pole becomes larger, phase margin is
14
Ultra-Low Noise, Low Power, Wideband Amplifier
The total noise due to the amplifier seen at the output of
the amplifier can be calculated by using the following
equation:
V ON =
2
R 1 2
R 1 2
R 1 2
 2 
 R 1

2
2 
2
2
BW ×  VN ×  1 + ------ + IN- × R 1 + IN+ × R 3 ×  1 + ------ + 4 × K × T × R 1 + 4 × K × T × R 2 ×  ------ + 4 × K × T × R3 ×  1 + ------ 
R 2
R 2
R 2 



 R 2

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 0.1µ F ceramic capacitor
across pins 7 (VS+) and pin 4 (VS-) will suffice.
As the above 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 root-mean-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
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.
The EL2125C 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 EL2125C an
ideal choice for RF, IF, and video applications. Furthermore, the EL2125C is current-limited at the output,
allowing it to withstand momentary short to ground.
However, the power dissipation with output-shorted
cannot exceed the power dissipation capability of the
package.
Supply Voltage Range and Single Supply
Operation
The EL2125C has been designed to operate with supply
voltage range of ±2.5V to ±15V. With a single supply,
the EL2125C 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.
Driving Cables and Capacitive Loads
Although the EL2125C is designed to drive low impedance load, capacitive loads will decreases the amplifier's
phase margin. As shown the 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 reflection-free performance.
When properly terminated, the capacitance of the coaxial cable will not add to the capacitive load seen by the
amplifier.
As the power supply voltage decreases from +30V to
+5V, it becomes necessary to pay special attention to the
input voltage range. The EL2125C 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 EL2125C has an input voltage range which
spans from 0.4V to 3.8V. The output range of the
EL2125C is also quite large, on a +5V supply, it swings
from 0.4V to 3.6V.
Power Supply Bypassing And Printed Circuit
Board Layout
As with any high frequency devices, good printed circuit
board layout is essential for optimum performance.
15
EL2125C
EL2125C
EL2125C
EL2125C
Ultra-Low Noise, Low Power, Wideband Amplifier
Effective May 15, 2002, Elantec, a leader in high performance analog products, is now a part of Intersil Corporation.
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.
November 14, 2002
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