View EL2125CSZ-T7_574783.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

(R)
EL2125
Data Sheet April 21, 2005 FN7045.2
Ultra-Low Noise, Low Power, Wideband Amplifier
The EL2125 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. The EL2125 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. The EL2125 is fabricated using Elantec's proprietary complementary bipolar process, and is specified for operation from -45C to +85C.
Features
* Voltage noise of only 0.83nV/Hz * Current noise of only 2.4pA/Hz * 200V offset voltage * 175MHz -3dB BW for AV = 10 * Low supply current - 10mA * SOT-23 package available * 2.5V to 15V operation * Pb-Free available (RoHS compliant)
Applications
* Ultrasound input amplifiers * Wideband instrumentation * Communication equipment * AGC & PLL active filters * Wideband sensors
Ordering Information
PART NUMBER EL2125CW-T7 EL2125CW-T7A EL2125CS EL2125CS-T7 EL2125CS-T13 EL2125CSZ (See Note) EL2125CSZ-T7 (See Note) EL2125CSZ-T13 (See Note) PACKAGE 5-Pin SOT-23 5-Pin SOT-23 8-Pin SO 8-Pin SO 8-Pin SO 8-Pin SO (Pb-free) 8-Pin SO (Pb-free) 8-Pin SO (Pb-free) TAPE & REEL 7" (3K pcs) 7" (250 pcs) 7" 13" 7" 13" PKG. DWG. # MDP0038 MDP0038 MDP0027 MDP0027 MDP0027 MDP0027 MDP0027 MDP0027
Pinouts
EL2125 (5-PIN SOT-23) TOP VIEW
OUT 1 VS- 2 IN+ 3 +4 IN5 VS+
EL2125 (8-PIN SO) TOP VIEW
NC 1 IN- 2 IN+ 3 VS- 4 + 8 NC 7 VS+ 6 OUT 5 NC
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.
1
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. 2003, 2005. All Rights Reserved All other trademarks mentioned are the property of their respective owners.
EL2125
Absolute Maximum Ratings (TA = 25C)
VS+ to VS- . . . . . . . . . . . . . . . . . . . . . . . . . . 33V Continuous Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . 40mA Any Input . . . . . . . . . . . . . . . . . . . . . . . . . . VS- - 0.3V to VS+ + 0.3V Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Curves Ambient Operating Temperature . . . . . . . . . . . . . . . .-45C to +85C Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . -65C to +150C Maximum Die Junction Temperature . . . . . . . . . . . . . . . . . . . +150C
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 DC PERFORMANCE VOS
VS = 5V, TA = 25C, RF = 180, RG = 20, RL = 500 unless otherwise specified. CONDITIONS MIN TYP MAX UNIT
DESCRIPTION
Input Offset Voltage (SO8) Input Offset Voltage (SOT23-5)
0.2
2 3
mV mV V/C A
TCVOS IB IOS TCIB CIN AVOL PSRR CMRR CMIR VOUTH VOUTL VOUTH2 VOUTL2 IOUT IS
Offset Voltage Temperature Coefficient Input Bias Current Input Bias Current Offset Input Bias Current Temperature Coefficient Input Capacitance Open Loop Gain Power Supply Rejection Ratio (Note 1) Common Mode Rejection Ratio Common Mode Input Range Output Voltage Swing High Output Voltage Swing Low Output Voltage Swing High Output Voltage Swing Low Output Short Circuit Current (Note 2) Supply Current No load, RF = 1k No load, RF = 1k RL = 100 RL = 100 80 3 at CMIR 80 80 80 -4.6 3.5 -30
1.8 -22 0.4 0.09 2.2 87 97 106 3.8 3.65 -3.87 3.3 -3.5 100 10.1 11 -3 -3.7 2
A A/C pF dB dB dB V V V V V mA mA
AC PERFORMANCE - RG = 20, CL = 5pF BW BW 0.1dB BW 1dB Peaking SR OS -3dB Bandwidth 0.1dB Bandwidth 1dB Bandwidth Peaking Slew Rate Overshoot, 4VP-P Output Square Wave VOUT = 2VP-P, measured at 20% to 80% Positive Negative tS VN Settling Time to 0.1% of 1V Pulse Voltage Noise Spectral Density 10kHz 150 175 34 150 0.4 185 0.6 2.7 42 0.83 MHz MHz MHz dB V/s % % ns nV/Hz
2
FN7045.2 April 21, 2005
EL2125
Electrical Specifications
PARAMETER IN HD2 HD3 NOTES: 1. Measured by moving the supplies from 4V to 6V 2. Pulse test only 3. Frequency = 1MHz, VOUT = 2VP-P, into 500 and 5pF load VS = 5V, TA = 25C, RF = 180, RG = 20, RL = 500 unless otherwise specified. (Continued) CONDITIONS 10kHz MIN TYP 2.4 -74 -91 MAX UNIT pA/Hz dBc dBc
DESCRIPTION Current Noise Spectral Density 2nd Harmonic Distortion (Note 3) 3rd Harmonic Distortion
Electrical Specifications
PARAMETER DC PERFORMANCE VOS
VS = 15V, TA = 25C, RF = 180, RG = 20, RL = 500 unless otherwise specified. CONDITIONS MIN TYP MAX UNIT
DESCRIPTION
Input Offset Voltage (SO8) Input Offset Voltage (SOT23-5)
0.6
3 3
mV mV V/C A
TCVOS IB IOS TCIB CIN AVOL PSRR CMRR CMIR VOUTH VOUTL VOUTH2 VOUTL2 IOUT IS
Offset Voltage Temperature Coefficient Input Bias Current Input Bias Current Offset Input Bias Current Temperature Coefficient Input Capacitance Open Loop Gain Power Supply Rejection Ratio (Note 1) Common Mode Rejection Ratio Common Mode Input Range Output Voltage Swing High Output Voltage Swing Low Output Voltage Swing High Output Voltage Swing Low Output Short Circuit Current (Note 2) Supply Current No load, RF = 1k No load, RF = 1k RL = 100 RL = 100 120 11 at CMIR 80 80 75 -14.6 13.35 -30
4.9 -24 0.4 0.08 2.2 87 97 105 13.8 13.5 -13.6 11.6 -10.4 250 10.8 12 -9.8 -13 2
A A/C pF dB dB dB V V V V V mA mA
AC PERFORMANCE - RG = 20, CL = 5pF BW BW 0.1dB BW 1dB Peaking SR OS tS VN -3dB Bandwidth 0.1dB Bandwidth 1dB Bandwidth Peaking Slew Rate Overshoot, 4VP-P Output Square Wave Settling Time to 0.1% of 1V Pulse Voltage Noise Spectral Density 10kHz VOUT = 2VP-P, measured at 20% to 80% 180 220 23 63 2.5 225 0.6 38 0.95 MHz MHz MHz dB V/s % ns nV/Hz
3
FN7045.2 April 21, 2005
EL2125
Electrical Specifications
PARAMETER IN HD2 HD3 NOTES: 1. Measured by moving the supplies from 13.5V to 16.5V 2. Pulse test only 3. Frequency = 1MHz, VOUT = 2VP-P, into 500 and 5pF load VS = 15V, TA = 25C, RF = 180, RG = 20, RL = 500 unless otherwise specified. (Continued) CONDITIONS 10kHz MIN TYP 2.1 -73 -96 MAX UNIT pA/Hz dBc dBc
DESCRIPTION Current Noise Spectral Density 2nd Harmonic Distortion (Note 3) 3rd Harmonic Distortion
Typical Performance Curves
5 NORMALIZED GAIN (dB) 5 NORMALIZED GAIN (dB) RF=499
VS=5V AV=10 RL=500 CL=5pF
RF=1k
VS=15V AV=10 RL=500 CL=5pF
RF=1k
RF=700
0 RF=180 RF=100 -5 1M
0 RF=499 RF=180 RF=100 -5 1M 10M FREQUENCY (Hz) 100M 300M
10M FREQUENCY (Hz)
100M 200M
FIGURE 1. NON-INVERTING FREQUENCY RESPONSE FOR VARIOUS RF
FIGURE 2. NON-INVERTING FREQUENCY RESPONSE FOR VARIOUS RF
6 RF=1k NORMALIZED GAIN (dB) 2 -2 -6 -10 -14 1M VS=5V AV=-10 RL=560 CL=5pF 10M FREQUENCY (Hz) NORMALIZED GAIN (dB) RF=499
6 2 -2 -6 -10 -14 1M VS=15V AV=-10 RL=500 CL=5pF 10M FREQUENCY (Hz) RF=1k RF=499
RF=350 RF=200 RF=97.6
RF=350 RF=200 RF=97.6
100M
300M
100M
300M
FIGURE 3. INVERTING FREQUENCY RESPONSE FOR VARIOUS RF
FIGURE 4. INVERTING FREQUENCY RESPONSE FOR VARIOUS RF
4
FN7045.2 April 21, 2005
EL2125 Typical Performance Curves
5 NORMALIZED GAIN (dB) NORMALIZED GAIN (dB) VS=5V RL=500 CL=5pF RG=20 AV=10
(Continued)
5 VS=15V RL=500 CL=5pF RF=700
AV=10
0
0 AV=20 AV=50
AV=50
AV=20
-5 1M
10M FREQUENCY (Hz)
100M 200M
-5 1M
10M FREQUENCY (Hz)
100M 200M
FIGURE 5. NON-INVERTING FREQUENCY RESPONSE vs GAIN
FIGURE 6. NON-INVERTING FREQUENCY RESPONSE FOR VARIOUS GAIN
6 NORMALIZED GAIN (dB) 2 -2 AV=-50 -6 VS=5V -10 RL=500 CL=5pF RG=35 -14 1M AV=-20 AV=-10 NORMALIZED GAIN (dB)
6 AV=-10 0 AV=-20 AV=-50 VS=15V RL=500 CL=5pF RG=50 -14 1M 10M FREQUENCY (Hz) 100M 300M
10M FREQUENCY (Hz)
100M
300M
FIGURE 7. INVERTING FREQUENCY RESPONSE vs GAIN
FIGURE 8. INVERTING FREQUENCY RESPONSE vs GAIN
5 NORMALIZED GAIN (dB)
NORMALIZED GAIN (dB)
VS=5V AV=10 RF=180 RL= 500 CL=5pF
6 3mVPP 250mVPP 0 3.3VPP VS=5V AV=-10 RF=350 RL= 500 CL=5pF -14 1M 2.5VPP 1VPP 30mVPP 500mVPP 4VPP 2VPP 1VPP 500mVPP
0
-5 1M
10M FREQUENCY (Hz)
100M 200M
10M FREQUENCY (Hz)
100M
300M
FIGURE 9. NON-INVERTING FREQUENCY RESPONSE FOR VARIOUS OUTPUT SIGNAL LEVELS
FIGURE 10. INVERTING FREQUENCY RESPONSE FOR VARIOUS OUTPUT SIGNAL LEVELS
5
FN7045.2 April 21, 2005
EL2125 Typical Performance Curves
5 NORMALIZED GAIN (dB) 3 1 -1 -3 -5 1M
(Continued)
NORMALIZED GAIN (dB)
VS=5V AV=10 RF=180 RL=500
5 CL=28.5pF CL=16pF
VS=5V AV=10 RF=700 RL=500
CL=17pF CL=11pF
0 CL=5pF CL=1.2pF
CL=5pF CL=1pF
10M FREQUENCY (Hz)
100M 200M
-5 1M
10M FREQUENCY (Hz)
100M 200M
FIGURE 11. NON-INVERTING FREQUENCY RESPONSE FOR VARIOUS CL
FIGURE 12. NON-INVERTING FREQUENCY RESPONSE FOR VARIOUS CL
6 NORMALIZED GAIN (dB)
CL=29.4pF NORMALIZED GAIN (dB) CL=16.4pF
6 2
CL=29.4pF CL=16.4pF
0 CL=11.4pF CL=5.1pF VS=5V AV=10 RF=350 RL=500 -14 1M 10M FREQUENCY (Hz) CL=1.2pF
-2 -6 -10 -14 1M VS=15V AV=10 RF=500 RL=500
CL=11.4pF CL=5.1pF CL=1.2pF
100M
300M
10M FREQUENCY (Hz)
100M
300M
FIGURE 13. INVERTING FREQUENCY RESPONSE FOR VARIOUS CL
FIGURE 14. INVERTING FREQUENCY RESPONSE FOR VARIOUS CL
100 OPEN LOOP GAIN (dB) 80 60 40 20 0 10K VS=5V 100K 1M 10M 100M GAIN PHASE
250 12 150 50 -50 PHASE () SUPPLY CURRENT (mA) 9.6 7.2 4.8 2.4 0
-150 -250 400M
0
3
6
9
12
15
FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
FIGURE 15. OPEN LOOP GAIN AND PHASE
FIGURE 16. SUPPLY CURRENT vs SUPPLY VOLTAGE
6
FN7045.2 April 21, 2005
EL2125 Typical Performance Curves
250 200 BANDWIDTH (MHz) 150 100 AV=-20 50 0 AV=20 AV=50 AV=-50 AV=10 PEAKING (dB) AV=-10
(Continued)
3 2.5 2 1.5 1 0.5 0 AV=-20 AV=20 AV=-50 10 12 AV=50 14 16 AV=10 AV=-10
2
4
6
8
10
12
14
16
2
4
6
8
VS (V)
VS (V)
FIGURE 17. 3dB BANDWIDTH vs SUPPLY VOLTAGE
FIGURE 18. PEAKING vs SUPPLY VOLTAGE
20mV/DIV
VINx2
20mV/DIV
VS=5V RL=500 RF=180 AV=10 CL=5pF
VS=15V RL=500 RF=180 AV=10 CL=5pF VINx2
VO
VO
10ns/DIV
10ns/DIV
FIGURE 19. SMALL SIGNAL STEP RESPONSE
FIGURE 20. SMALL SIGNAL STEP RESPONSE
OUTPUT VOLTAGE (0.5V/DIV)
TIME (20ns/DIV)
OUTPUT VOLTAGE (0.5V/DIV)
VS=5V RL=500 RF=180 AV=10 CL=5pF
VS=15V RL=500 RF=180 AV=10 CL=5pF
TIME (20ns/DIV)
FIGURE 21. LARGE SIGNAL STEP RESPONSE
FIGURE 22. LARGE SIGNAL STEP RESPONSE
7
FN7045.2 April 21, 2005
EL2125 Typical Performance Curves
-40 -50 DISTORTION (dBc) -60 -70 -80 -90 -100 -110 0 1 2 3 4 5 6 7 3RD HD
(Continued)
DISTORTION (dBc)
VS=5V RF=180 AV=10 RL=500 2ND HD
-30 -40 -50 -60 -70 -80 -90 -100 -110 0
VS=15V RF=180 AV=10 RL=500
2ND HD
3RD HD
5
10
15
20
25
VOUT (VPP)
VOUT (VPP)
FIGURE 23. 1MHz HARMONIC DISTORTION vs OUTPUT SWING
FIGURE 24. 1MHz HARMONIC DISTORTION vs OUTPUT SWING
-30 -40 -50 -60 -70 -80 -90 1K
VOLTAGE NOISE (nV/Hz), CURRENT NOISE (pA/Hz)
THD (dBc)
VS=5V VO=2VPP AV=10 RF=180 RL=500
100
10 IN, VS=5V 1 VN, VS=15V VN, VS=5V IN, VS=15V
10K
100K
1M
10M
100M
0.1 10
100
1K FREQUENCY (Hz)
10K
100K
FREQUENCY (Hz)
FIGURE 25. TOTAL HARMONIC DISTORTION vs FREQUENCY
FIGURE 26. VOLTAGE AND CURRENT NOISE vs FREQUENCY
60 50 SETTLING TIME (ns) 40 30 20 10 0 0.1 VS=5V VO=2VPP VS=15V VO=5VPP VS=5V VO=5VPP GROUP DELAY (ns)
14 10 6 2 -2 -6
VS=15V
AV=20
AV=10
VS=15V VO=2VPP
1 ACCURACY (%)
10
1
10 FREQUENCY (MHz)
100
400
FIGURE 27. SETTLING TIME vs ACCURACY
FIGURE 28. GROUP DELAY
8
FN7045.2 April 21, 2005
EL2125 Typical Performance Curves
-10 -30 CMRR (dB) PSRR (dB) -50 -70 -99 -110 10
(Continued)
110 90 PSRR70 PSRR+ 50 30 10 10K
100
1K
10K
100K
1M
10M 100M
100K
1M
10M
100M
600M
FREQUENCY (Hz)
FREQUENCY (Hz)
FIGURE 29. CMRR
FIGURE 30. PSRR
100 -3dB BANDWIDTH (MHz)
200 160 120 PEAKING 80 40 0 -40 BANDWIDTH
3.5 3 PEAKING (dB) 2.5 2 1.5 1 0.5 0 40 80 120 0 160
10 ROUT () 1 0.1
0.01 0.001 10K
100K
1M FREQUENCY (Hz)
10M
100M
TEMPERATURE (C)
FIGURE 31. CLOSED LOOP OUTPUT IMPEDANCE vs FREQUENCY
FIGURE 32. BANDWIDTH vs TEMPERATURE
350 300 SLEW RATE (V/s) 250 200 150 100 5VSR-
13
15VSRIS (mA)
12
11
VS=15V
5VSR+
10 15VSR+ 10 15 20 9 -50 0
VS=5V
0
5
50
100
150
VOUT SWING (VPP)
DIE TEMPERATURE (C)
FIGURE 33. SLEW RATE vs SWING
FIGURE 34. SUPPLY CURRENT vs TEMPERATURE
9
FN7045.2 April 21, 2005
EL2125 Typical Performance Curves
0 VS=5V -15 -1 VOS (mV) IB+ (A) 100 150 VS=15V
(Continued)
-10
-20
-2 -25
-3 -50
0
50
-30 -50
0
50
100
150
DIE TEMPERATURE (C)
DIE TEMPERATURE (C)
FIGURE 35. OFFSET VOLTAGE vs TEMPERATURE
FIGURE 36. INPUT BIAS CURRENT vs TEMPERATURE
120 VS=15V
110 VS=5V
CMRR (dB)
PSRR (dB)
100
100
VS=15V 90
80
VS=5V
60 -50
0
50
100
150
80 -50
0
50
100
150
DIE TEMPERATURE (C)
DIE TEMPERATURE (C)
FIGURE 37. CMRR vs TEMPERATURE
FIGURE 38. PSRR vs TEMPERATURE
240
VO=2VPP
3.9 VS=15V 3.8 VOUTH (V)
220 SR (V/s)
200 VS=5V 180
3.7
VS=5V
3.6
160 -50
0
50
100
150
3.5 -50
0
50
100
150
DIE TEMPERATURE (C)
DIE TEMPERATURE (C)
FIGURE 39. SLEW RATE vs TEMPERATURE
FIGURE 40. POSITIVE OUTPUT SWING vs TEMPERATURE
10
FN7045.2 April 21, 2005
EL2125 Typical Performance Curves
13.6
(Continued)
-9.75
VS=15V VOUTH (V) VOUTL (V) 13.5
-9.8 VS=5V -9.85
-9.9
13.4 -50
0
50
100
150
-9.95 -50
0
50
100
150
DIE TEMPERATURE (C)
DIE TEMPERATURE (C)
FIGURE 41. POSITIVE OUTPUT SWING vs TEMPERATURE
FIGURE 42. NEGATIVE OUTPUT SWING vs TEMPERATURE
-13.4
-3.42 -3.44 VS=15V VOUTL2 (V)
VOUTL (V)
-13.5
-3.46 -3.48 -3.5
VS=5V
-13.6
-13.7 -50
0
50
100
150
-3.52 -50
0
50
100
150
DIE TEMPERATURE (C)
DIE TEMPERATURE (C)
FIGURE 43. NEGATIVE OUTPUT SWING vs TEMPERATURE
FIGURE 44. LOADED NEGATIVE OUTPUT SWING vs TEMPERATURE
-9.6 -9.8 VOUTH2 (V) -10 -10.2 -10.4 -10.6 -10.8 -50 VS=15V
3.35
VOUTL2 (V)
VS=5V 3.3
0
50
100
150
3.25 -50
0
50
100
150
DIE TEMPERATURE (C)
DIE TEMPERATURE (C)
FIGURE 45. NEGATIVE OUTPUT SWING vs TEMPERATURE
FIGURE 46. LOADED POSITIVE OUTPUT SWING vs TEMPEARTURE
11
FN7045.2 April 21, 2005
EL2125 Typical Performance Curves
12 1.2 VS=15V VOUTH2 (V) 11.6 11.4 11.2 11 -50 POWER DISSIPATION (W) 11.8 1 0.8 0.6 0.4 488mW 0.2 0 SOT23-5 JA=256C/W 0 25 50 75 85 100 125 150 781mW SO8 JA=160C/W
(Continued)
JEDEC JESD51-3 LOW EFFECTIVE THERMAL CONDUCTIVITY TEST BOARD
0
50
100
150
DIE TEMPERATURE (C)
AMBIENT TEMPERATURE (C)
FIGURE 47. LOADED POSITIVE OUTPUT SWING vs TEMPERATURE
FIGURE 48. PACKAGE POWER DISSIPATION vs AMBIENT TEMPERATURE
1.8 POWER DISSIPATION (W) 1.6 1.4
JEDEC JESD51-7 HIGH EFFECTIVE THERMAL CONDUCTIVITY TEST BOARD
1.2 1.136W 1 0.8 0.6 543mW 0.4 0.2 0 0 SOT23-5 JA=230C/W 25 50
SO8 JA=110C/W
75 85 100
125
150
AMBIENT TEMPERATURE (C)
FIGURE 49. PACKAGE POWER DISSIPATION vs AMBIENT TEMPERATURE
12
FN7045.2 April 21, 2005
EL2125 Pin Descriptions
5-PIN SOT-23 1 8-PIN SO 6 PIN NAME VOUT PIN FUNCTION Output EQUIVALENT CIRCUIT
VS+
VOUT
CIRCUIT 1
2 3
4 3
VSVINA+
Supply Input
VS+
VIN+
VIN-
VSCIRCUIT 2
4 5
2 7
VINAVS+
Input Supply
Reference Circuit 2
Applications Information
Product Description
The EL2125 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, 200V 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 EL2125 also has excellent DC specifications: 200V VOS, 22A IB, 0.4A IOS, and 106dB CMRR. These specifications allow the EL2125 to be used in DC-sensitive applications such as difference amplifiers.
compensation, the device can also operate at lower gain settings. The RC network shown in Figure 50 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 2RC must be less than 400MHz.
RF R C VIN + VOUT
FIGURE 50.
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 the in typical performance curves section of this data sheet.
Gain-Bandwidth Product
The EL2125 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 closed-loop bandwidths. For example, the EL2125 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 EL2125 is designed for gain > 10 with external
13
FN7045.2 April 21, 2005
EL2125
Noise Calculations
The primary application for the EL2125 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 51 below shows all the noise sources for all the components around the amplifier.
VIN R3 VR3 IN+ VR1 VN + R1 VON
limited 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 EL2125 is designed to drive low impedance load, capacitive loads will decrease 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 5 to 20. 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.
IN-
VR2 R2
FIGURE 51.
* 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 = 4kTRx
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 4.7F tantalum capacitor in parallel with 0.1F 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 4.7F tantalum capacitor in parallel with a 0.1F 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.
where: * k is Boltzmann's constant = 1.380658 x 10-23 * T is temperature in degrees Kelvin (273+ C) The total noise due to the amplifier seen at the output of the amplifier can be calculated by using the equation below (Figure 52). 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.
Supply Voltage Range and Single Supply Operation
The EL2125 has been designed to operate with supply voltage range of 2.5V to 15V. With a single supply, the EL2125 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
Output Drive Capability
The EL2125 is designed to drive low impedance load. It can easily drive 6VP-P signal into a 100 load. This high output drive capability makes the EL2125 an ideal choice for RF, IF, and video applications. Furthermore, the EL2125 is current-
V ON =
R 1 2 R 1 2 R 1 2 R 1 2 2 2 2 2 2 BW x VN x 1 + ------ + IN- x R 1 + IN+ x R 3 x 1 + ------ + 4 x K x T x R 1 + 4 x K x T x R 2 x ------ + 4 x K x T x R 3 x 1 + ------ R 2 R 2 R 2 R 2 FIGURE 52.
14
FN7045.2 April 21, 2005
EL2125
voltage range. The EL2125 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 EL2125 has an input voltage range which spans from 0.4V to 3.8V. The output range of the EL2125 is also quite large, on a +5V supply, it swings from 0.4V to 3.6V.
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.
For information regarding Intersil Corporation and its products, see www.intersil.com 15
FN7045.2 April 21, 2005

▲Up To Search▲

Price & Availability of EL2125CSZ-T7

	To Download EL2125CSZ-T7 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .