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1.8 V, Micropower, Zero-Drift, Rail-to-Rail Input/Output Op Amp ADA4051-2
FEATURES
Very low supply current: 13 A Low offset voltage: 15 V maximum Offset voltage drift: 20 nV/C Single-supply operation: 1.8 V to 5.5 V High PSRR: 110 dB minimum High CMRR: 110 dB minimum Rail-to-rail input and output Unity gain stable Extended industrial temperature range
PIN CONFIGURATION
OUT A 1 -IN A 2 +IN A 3 V- 4
8
V+ OUT B
08056-001
ADA4051-2
TOP VIEW (Not to Scale)
7 6 5
-IN B +IN B
Figure 1. 8-Lead MSOP (RM-8)
APPLICATIONS
Pressure and position sensors Temperature measurements Electronic scales Medical instrumentation Battery-powered equipment Handheld test equipment
GENERAL DESCRIPTION
The ADA4051-2 is a CMOS, micropower, zero-drift operational amplifier utilizing an innovative chopping technique. This amplifier features rail-to-rail input and output swing and extremely low offset voltage while operating from a 1.8 V to 5.5 V power supply. This amplifier also offers high PSRR and CMRR, while operating with a supply current of only 13 A per amplifier. This combination of features makes the ADA4051-2 amplifier an ideal choice for battery-powered applications where high precision as well as low power consumption is important. The ADA4051-2 is specified for the extended industrial temperature range of -40C to +125C. The ADA4051-2 amplifier is available in the standard 8-pin MSOP. The ADA4051-2 is a member of a growing series of zero-drift op amps offered by Analog Devices, Inc. Refer to Table 1 for a list of these devices. Table 1. Op Amps
Supple Single Dual Quad Low Power, 5 V AD8538 AD8539 5V AD8628 AD8629 AD8630 16 V AD8638 AD8639
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other 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. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2009 Analog Devices, Inc. All rights reserved.
ADA4051-2 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications ....................................................................................... 1 Pin Configuration ............................................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Electrical Characteristics--5 V Operation................................ 3 Electrical Characteristics--1.8 V Operation ............................ 4 Absolute Maximum Ratings............................................................ 5 Thermal Resistance .......................................................................5 Power Sequencing .........................................................................5 ESD Caution...................................................................................5 Typical Performance Characteristics ..............................................6 Theory of Operation ...................................................................... 15 Input Voltage Range ................................................................... 16 Output Phase Reversal ............................................................... 17 Outline Dimensions ....................................................................... 18 Ordering Guide .......................................................................... 18
REVISION HISTORY
7/09--Revision 0: Initial Version
Rev. 0 | Page 2 of 20
ADA4051-2 SPECIFICATIONS
ELECTRICAL CHARACTERISTICS--5 V OPERATION
VSY = 5.0 V, VCM = VSY/2 V, TA = 25C, unless otherwise noted. Table 2.
Parameter INPUT CHARACTERISTICS Offset Voltage Offset Voltage Drift Input Bias Current Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Large-Signal Voltage Gain Input Resistance Input Capacitance, Differential Mode Input Capacitance, Common Mode OUTPUT CHARACTERISTICS Output Voltage High Symbol VOS VOS/T IB IOS -40C TA +125C -40C TA +125C 0 V VCM 5 V -40C TA +125C RL = 10 k, 0.1 V VOUT VSY - 0.1 V -40C TA +125C 0 110 106 115 106 Conditions 0 V VCM 5 V -40C TA +125C -40C TA +125C 40 Min Typ 2 0.02 20 Max 15 0.1 70 200 100 150 5 Unit V V/C pA pA pA pA V dB dB dB dB M pF pF V V V V mV mV mV mV mA dB dB A A V/s V/s s kHz Degrees dB V p-p nV/Hz fA/Hz
CMRR AVO RIN CINDM CINCM VOH
135 135 8 2 5
Output Voltage Low
VOL
Short-Circuit Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current per Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Gain Bandwidth Product Phase Margin Channel Separation NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density
ISC ZOUT PSRR ISY
RL = 10 k to VCM -40C TA +125C RL = 100 k to VCM -40C TA +125C RL = 10 k to VCM -40C TA +125C RL = 100 k to VCM -40C TA +125C VOUT = VSY or GND f = 1 kHz, G = 10 1.8 V VSY 5.5 V -40C TA +125C VOUT = VSY/2 -40C TA +125C RL = 10 k, CL = 100 pF, G = 1 RL = 10 k, CL = 100 pF, G = 1 To 0.1%, VIN = 1 V p-p, RL = 10 k, CL = 100 pF CL = 100 pF, G = 1 CL = 100 pF, G = 1 VIN = 4.99 V, f = 100 Hz f = 0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz
4.96 4.9 4.996 4.985
4.99 4.998 9 1 15 1 30 90 4 13
110 106
135 13 17 20
SR+ SR- tS GBP M CS en p-p en in
0.06 0.04 110 125 40 140 1.96 95 100
Rev. 0 | Page 3 of 20
ADA4051-2
ELECTRICAL CHARACTERISTICS--1.8 V OPERATION
VSY = 1.8 V, VCM = VSY/2 V, TA = 25C, unless otherwise noted. Table 3.
Parameter INPUT CHARACTERISTICS Offset Voltage Offset Voltage Drift Input Bias Current Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Large-Signal Voltage Gain Input Resistance Input Capacitance, Differential Mode Input Capacitance, Common Mode OUTPUT CHARACTERISTICS Output Voltage High Symbol VOS VOS/T IB IOS -40C TA +125C -40C TA +125C 0 V VCM 1.8 V -40C TA +125C RL = 10 k, 0.1 V VOUT VSY - 0.1 V -40C TA +125C 0 105 100 106 100 Conditions 0 V VCM 1.8 V -40C TA +125C -40C TA +125C 10 Min Typ 2 0.02 5 Max 15 0.1 50 200 100 150 1.8 Unit V V/C pA pA pA pA V dB dB dB dB M pF pF V V V V mV mV mV mV mA dB dB A A V/s V/s s kHz Degrees dB V p-p nV/Hz fA/Hz
CMRR AVO RIN CINDM CINCM VOH
125 130 8 2 5
Output Voltage Low
VOL
Short-Circuit Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current per Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Gain Bandwidth Product Phase Margin Channel Separation NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density
ISC ZOUT PSRR ISY
RL = 10 k to VCM -40C TA +125C RL = 100 k to VCM -40C TA +125C RL = 10 k to VCM -40C TA +125C RL = 100 k to VCM -40C TA +125C VOUT = VSY or GND f = 1 kHz, G = 10 1.8 V VSY 5.5 V -40C TA +125C VOUT = VSY/2 -40C TA +125C RL = 10 k, CL = 100 pF, G = 1 RL = 10 k, CL = 100 pF, G = 1 To 0.1%, VIN = 1 V p-p, RL = 10 k, CL = 100 pF CL = 100 pF, G = 1 CL = 100 pF, G = 1 VIN = 1.7 V, f = 100 Hz f = 0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz
1.76 1.7 1.796 1.79
1.796 1.799 3 1 13 1 20 40 3 9
110 106
135 13 17 20
SR+ SR- tS GBP M CS en p-p en in
0.04 0.03 120 115 40 140 1.96 95 100
Rev. 0 | Page 4 of 20
ADA4051-2 ABSOLUTE MAXIMUM RATINGS
Table 4.
Parameter Supply Voltage Input Voltage Input Current1 Differential Input Voltage2 Output Short-Circuit Duration to GND Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature (Soldering, 60 sec)
1
THERMAL RESISTANCE
Rating 6V VSY 0.3 V 10 mA VSY Indefinite -65C to +150C -40C to +125C -65C to +150C 300C
JA is specified with the device soldered on a circuit board with its exposed paddle soldered to a pad (if applicable) on a 4-layer JEDEC standard PC board with zero air flow, unless otherwise specified. Table 5. Thermal Resistance
Package Type 8-Lead MSOP (RM-8) JA 186 JC 52 Unit C/W
POWER SEQUENCING
The op amp supplies must be established simultaneously with, or before, any input signals are applied. If this is not possible, the input current must be limited to 10 mA.
The input pins have clamp diodes to the power supply pins. Limit input current to 10 mA or less whenever input signals exceed the power supply rail by 0.3 V. 2 Inputs are protected against high differential voltages by internal series 1.33 k resistors and back-to-back diode-connected N-MOSFETs (with a typical VT of 0.7 V for VCM of 0 V).
ESD CAUTION
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Rev. 0 | Page 5 of 20
ADA4051-2 TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25C, unless otherwise noted.
300 VSY = 1.8V VCM = VSY/2 250 NUMBER OF AMPLIFIERS
NUMBER OF AMPLIFIERS
300
VSY = 5V VCM = VSY/2
250
200
200
150
150
100
100
50
50
VOS (V)
VOS (V)
Figure 2. Input Offset Voltage Distribution
10
VSY = 1.8V -40C TA +125C
Figure 5. Input Offset Voltage Distribution
8 VSY = 5V -40C TA 125C
8
NUMBER OF AMPLIFIERS
6
NUMBER OF AMPLIFIERS
6
4
4
2
2
0
08056-003
TCVOS (V/C)
TCVOS (V/C)
Figure 3. Input Offset Voltage Drift Distribution with Temperature
Figure 6. Input Offset Voltage Drift Distribution with Temperature
15 VSY = 1.8V 10
15 VSY = 5V 10
5
5
VOS (V)
VOS (V)
0 DEVICE 1 DEVICE 2 DEVICE 3 DEVICE 4 DEVICE 5 DEVICE 6 DEVICE 7 DEVICE 8 DEVICE 9 DEVICE 10
08056-004
0 DEVICE 1 DEVICE 2 DEVICE 3 DEVICE 4 DEVICE 5 DEVICE 6 DEVICE 7 DEVICE 8 DEVICE 9 DEVICE 10
08056-007
-5
-5
-10
-10
-15
0
0.3
0.6
0.9 VCM (V)
1.2
1.5
1.8
-15
0
1
2 VCM (V)
3
4
5
Figure 4. Input Offset Voltage vs. Input Common-Mode Voltage
Figure 7. Input Offset Voltage vs. Input Common-Mode Voltage
Rev. 0 | Page 6 of 20
08056-006
0
0.01 0.02 0.03 0.04 0.05
0.06 0.07 0.08 0.09 0.10
0
0
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
08056-005
-10
-8
-6
-4
-2
0
2
4
6
8
10
08056-002
0
0
-10
-8
-6
-4
-2
0
2
4
6
8
10
ADA4051-2
TA = 25C, unless otherwise noted.
100
VSY = 1.8V IB+ IB-
100
VSY = 5V IB+ IB-
80
80
60
60 IB (pA)
08056-008
IB (pA)
40
40
20
20
0
0
25
50
75 TEMPERATURE (C)
100
125
25
50
75 TEMPERATURE (C)
100
125
Figure 8. Input Bias Current vs. Temperature
200 150 100 50
Figure 11. Input Bias Current vs. Temperature
400 300 200 100
IB (pA)
VSY = 1.8V
VSY = 5V
IB (pA)
0 -50 -100 -150 -200 IB+, 25C IB-, 25C IB+, 85C IB-, 85C IB+, 125C IB-, 125C
08056-009
0 -100 -200 -300 -400
IB+, 25C IB-, 25C IB+, 85C IB-, 85C IB+, 125C IB-, 125C
08056-012
08056-013
0
0.3
0.6
0.9 VCM (V)
1.2
1.5
1.8
0
0.5
1.0
1.5
2.0
2.5 VCM (V)
3.0
3.5
4.0
4.5
5.0
Figure 9. Input Bias Current vs. Common-Mode Voltage and Temperature
10,000 VSY = 1.8V
Figure 12. Input Bias Current vs. Common-Mode Voltage and Temperature
10,000
OUTPUT VOLTAGE (VOH) TO SUPPLY RAIL (mV)
OUTPUT VOLTAGE (VOH) TO SUPPLY RAIL (mV)
VSY = 5V
1000
1000
100
100
10
10
1
1
0.1
0.01
0.1 LOAD CURRENT (mA)
1
10
08056-010
0.01 0.001
-40C +25C +85C +125C
0.1
0.01 0.001
-40C +25C +85C +125C
0.01
0.1
1
10
100
LOAD CURRENT (mA)
Figure 10. Output Voltage (VOH) to Supply Rail vs. Load Current and Temperature
Figure 13. Output Voltage (VOH) to Supply Rail vs. Load Current and Temperature
Rev. 0 | Page 7 of 20
08056-011
-20
-20
ADA4051-2
TA = 25C, unless otherwise noted.
OUTPUT VOLTAGE (VOL) TO SUPPLY RAIL (mV) OUTPUT VOLTAGE (VOL) TO SUPPLY RAIL (mV)
10,000
VSY = 1.8V
10,000
VSY = 5V
1000
1000
100
100
10
10
1
1
0.1
0.01
0.1
1
10
100
08056-014
0.01
0.1
1
10
100
LOAD CURRENT (mA)
LOAD CURRENT (mA)
Figure 14. Output Voltage (VOL) to Supply Rail vs. Load Current and Temperature
Figure 17. Output Voltage (VOL) to Supply Rail vs. Load Current and Temperature
1800 RL = 100k OUTPUT VOLTAGE [VOH] (mV)
5000 4998 4996 4994 4992 4990 4988 4986 4984
08056-015
RL = 100k
1799
OUTPUT VOLTAGE [VOH] (mV)
1798
1797
RL = 10k
RL = 10k
1796
1795 VSY = 1.8V VCM = VSY/2 -25 -10 5 20 35 50 65 80 95 110 125 VSY = 5V VCM = VSY/2 4982 -40 -25 -10
5
20
35
50
65
80
95
110
125
TEMPERATURE (C)
TEMPERATURE (C)
Figure 15. Output Voltage (VOH) vs. Temperature
Figure 18. Output Voltage (VOH) vs. Temperature
14 12
OUTPUT VOLTAGE [VOL] (mV)
VSY = 1.8V VCM = VSY/2
OUTPUT VOLTAGE [VOL] (mV)
14 12 10 8 6 4 2 RL = 100k
08056-016
VSY = 5V VCM = VSY/2
10 8 6 4 2 0 -40
RL = 10k
RL = 10k
RL = 100k -25 -10 5 20 35 50 65 80 95 110 125
08056-019
-25
-10
5
20
35
50
65
80
95
110
125
0 -40
TEMPERATURE (C)
TEMPERATURE (C)
Figure 16. Output Voltage (VOL) vs. Temperature
Figure 19. Output Voltage (VOL) vs. Temperature
Rev. 0 | Page 8 of 20
08056-018
1794 -40
08056-017
0.01 0.001
-40C +25C +85C +125C
0.1
0.01 0.001
-40C +25C +85C +125C
ADA4051-2
TA = 25C, unless otherwise noted.
30
+125C +85C +25C -40C
TOTAL SUPPLY CURRENT (A)
30
VCM = VSY/2
VSY = 5V VSY = 1.8V
25
TOTAL SUPPLY CURRENT (A)
25
20
20
15
15
10
10
5
VCM = VSY/2 -40C TA 125C 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
08056-020
5
-25
-10
5
20
35
50
65
80
95
110
125
SUPPLY VOLTAGE (V)
TEMPERATURE (C)
Figure 20. Total Supply Current vs. Supply Voltage and Temperature
Figure 23. Total Supply Current vs. Temperature
80 60
OPEN-LOOP GAIN (dB)
180 VSY = 1.8V CL= 100pF 135 90
PHASE (Degrees)
80 60 VSY = 5V CL= 100pF
180 135 90 PHASE GAIN 45 0 -45 -90 -135
08056-025 08056-062
OPEN-LOOP GAIN (dB)
40 20 GAIN 0 -20 -40 -60 100 PHASE
40 20 0 -20 -40 -60 100
45 0 -45 -90 -135
FREQUENCY (Hz)
08056-022
1k
10k
100k
1M
1k
10k FREQUENCY (Hz)
100k
1M
Figure 21. Open-Loop Gain and Phase vs. Frequency
Figure 24. Open-Loop Gain and Phase vs. Frequency
50 40 30 CLOSED-LOOP GAIN (dB)
50 VSY = 1.8V RL = 10k CL = 50pF 40 30
VSY = 5V RL = 10k CL = 50pF
CLOSED-LOOP GAIN (dB)
20 10 0 -10 -20 -30 -40 -50 100 G=1 G = 10 G = 100
08056-061
20 10 0 -10 -20 -30 -40 G=1 G = 10 G = 100 1k 10k FREQUENCY (Hz) 100k 1M
1k
10k FREQUENCY (Hz)
100k
1M
-50 100
Figure 22. Closed-Loop Gain vs. Frequency
Figure 25. Closed-Loop Gain vs. Frequency
Rev. 0 | Page 9 of 20
PHASE (Degrees)
08056-023
0
0 -40
ADA4051-2
TA = 25C, unless otherwise noted.
10k
VSY = 1.8V
10k
VSY = 5V
1k
1k
ZOUT ()
ZOUT ()
G = -1 G = -10 G = -100 10k 100k 1M
08056-026
100
100
10
10
1
1 G = -1 G = -10 G = -100 10k 100k 1M
08056-029 08056-031 08056-030
0.1 1k
0.1 1k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 26. Output Impedance vs. Frequency
110
VSY = 1.8V
110
Figure 29. Output Impedance vs. Frequency
VSY = 5V 100 90
100 90
CMRR (dB) CMRR (dB)
80 70 60 50 40 10
80 70 60 50 40 10
100
1k
10k
100k
1M
08056-027
100
1k
10k
100k
1M
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 27. CMRR vs. Frequency
Figure 30. CMRR vs. Frequency
120 VSY = 1.8V 100
120 VSY = 5V 100
80
80
PSRR (dB)
PSRR (dB)
60 PSRR+ 40
60 PSRR+ 40
20 PSRR- 1k 10k FREQUENCY (Hz) 100k 1M
08056-028
20 PSRR- 0 100 1k 10k FREQUENCY (Hz) 100k 1M
0 100
Figure 28. PSRR vs. Frequency
Figure 31. PSRR vs. Frequency
Rev. 0 | Page 10 of 20
ADA4051-2
TA = 25C, unless otherwise noted.
60
VSY = 0.9V VIN = 50mV p-p RL = 10k CL= 50pF
60
50
50
VSY = 2.5V VIN = 50mV p-p RL = 10k CL= 50pF
OVERSHOOT (%)
OVERSHOOT (%)
40
40
-OVERSHOOT
30
30
20
-OVERSHOOT +OVERSHOOT
20
+OVERSHOOT
10
10
08056-032
100
LOAD CAPACITANCE (pF)
100
LOAD CAPACITANCE (pF)
Figure 32. Small-Signal Overshoot vs. Load Capacitance
Figure 35. Small-Signal Overshoot vs. Load Capacitance
VSY = 1.8V RL = 10k CL = 100pF G=1 VIN = 1.5V p-p
VOLTAGE (500mV/DIV)
VOLTAGE (1V/DIV)
VSY = 5V RL = 10k CL = 100pF G=1 VIN = 4V p-p
08056-033
TIME (100s/DIV)
TIME (100s/DIV)
Figure 33. Large-Signal Transient Response
Figure 36. Large Signal Transient Response
VSY = 1.8V RL = 10k CL = 100pF G=1 VIN = 50mV p-p
VOLTAGE (10mV/DIV)
VOLTAGE (10mV/DIV)
VSY = 5V RL = 10k CL = 100pF G=1 VIN = 50mV p-p
08056-034
TIME (100s/DIV)
TIME (100s/DIV)
Figure 34. Small-Signal Transient Response
Figure 37. Small Signal Transient Response
Rev. 0 | Page 11 of 20
08056-037
08056-036
08056-035
0 10
0 10
ADA4051-2
TA = 25C, unless otherwise noted.
VSY = 1.8V
INPUT VOLTAGE NOISE (0.5V/DIV)
INPUT VOLTAGE NOISE (0.5V/DIV)
VSY = 5V
1.94V p-p
1.96V p-p
08056-038
TIME (4s/DIV)
TIME (4s/DIV)
Figure 38. Input Voltage Noise 0.1 Hz to 10 Hz
1k
1k
Figure 41. Input Voltage Noise 0.1 Hz to 10 Hz
VSY = 1.8V
VOLTAGE NOISE DENSITY (nV/Hz)
VSY = 5V
VOLTAGE NOISE DENSITY (nV/Hz)
100
100
10
10
100 FREQUENCY (Hz)
1k
10k
100 FREQUENCY (Hz)
1k
10k
Figure 39. Voltage Noise Density vs. Frequency
0.15 0.10 VSY = 0.9V G = -10
Figure 42. Voltage Noise Density vs. Frequency
0.4 0.3 VSY = 2.5V G = -10
OUTPUT VOLTAGE (1V/DIV)
08056-043
OUTPUT VOLTAGE (500mV/DIV)
INPUT VOLTAGE (100mV/DIV)
INPUT VOLTAGE (50mV/DIV)
0.05 INPUT VOLTAGE 0 -0.05 OUTPUT VOLTAGE 0.5 0 -0.5 -1.0
0.2 0.1 0 -0.1 INPUT VOLTAGE OUTPUT VOLTAGE 1 0 -1 -2
08056-040
TIME (40s/DIV)
-1.5
TIME (40s/DIV)
-3
Figure 40. Positive Overload Recovery
Figure 43. Positive Overload Recovery
Rev. 0 | Page 12 of 20
08056-042
08056-039
1 10
1 10
08056-041
ADA4051-2
TA = 25C, unless otherwise noted.
0.05 0 INPUT VOLTAGE
0.1 0
OUTPUT VOLTAGE (500mV/DIV)
INPUT VOLTAGE (100mV/DIV)
INPUT VOLTAGE
OUTPUT VOLTAGE (1V/DIV)
INPUT VOLTAGE (50mV/DIV)
-0.05 -0.10 -0.15 1.5 1.0 0.5 OUTPUT VOLTAGE VSY = 0.9V G = -10 TIME (40s/DIV) 0
-0.1 -0.2 -0.3 -0.4 4 3 2 1 OUTPUT VOLTAGE 0 -1
-0.5
08056-044
TIME (40s/DIV)
Figure 44. Negative Overload Recovery
Figure 47. Negative Overload Recovery
INPUT VOLTAGE
INPUT VOLTAGE
OUTPUT VOLTAGE (5mV/DIV)
5 ERROR BAND OUTPUT VOLTAGE 0 -5 VSY = 0.9V VIN = 1V p-p RL = 10k CL = 100pF TIME (40s/DIV)
5 ERROR BAND OUTPUT VOLTAGE 0 -5
08056-045
TIME (40s/DIV)
Figure 45. Positive Settling Time to 0.1%
Figure 48. Positive Settling Time to 0.1%
OUTPUT VOLTAGE (5mV/DIV)
INPUT VOLTAGE (500mV/DIV)
INPUT VOLTAGE
INPUT VOLTAGE
5 ERROR BAND OUTPUT VOLTAGE 0 -5 VSY = 0.9V VIN = 1V p-p RL = 10k CL = 100pF TIME (40s/DIV)
5 ERROR BAND OUTPUT VOLTAGE 0 -5 VSY = 2.5V VIN = 1V p-p RL = 10k CL = 100pF TIME (40s/DIV)
08056-046
OUTPUT VOLTAGE (5mV/DIV)
08056-049
Figure 46. Negative Settling Time to 0.1%
INPUT VOLTAGE (500mV/DIV)
Figure 49. Negative Settling Time to 0.1%
Rev. 0 | Page 13 of 20
08056-048
VSY = 2.5V VIN = 1V p-p RL = 10k CL = 100pF
OUTPUT VOLTAGE (5mV/DIV)
INPUT VOLTAGE (500mV/DIV)
INPUT VOLTAGE (500mV/DIV)
08056-047
VSY = 2.5V G = -10
ADA4051-2
TA = 25C, unless otherwise noted.
-100
-100
100k 1k VIN = 0.5V VIN = 1V VIN = 1.7V
100k 1k
CHANNEL SEPARATION (dB)
VIN = 1V VIN = 3V VIN = 4.99V
CHANNEL SEPARATION (dB)
-110
-110
-120
-120
-130
-130
-140
200
2k
FREQUENCY (Hz)
20k
08056-050
200
2k FREQUENCY (Hz)
20k
Figure 50. Channel Separation vs. Frequency
1.8
Figure 53. Channel Separation vs. Frequency
6
1.5
5
OUTPUT SWING (V)
OUTPUT SWING (V)
1.2
4
0.9
3
0.6 VSY = 1.8V VIN = 1.7V G=1 RL= 10k CL = 50pF 1k 10k FREQUENCY (Hz) 100k
08056-051
2 VSY = 5V VIN = 4.9V G=1 RL= 10k CL = 50pF 1k 10k FREQUENCY (Hz) 100k
08056-054
0.3
1
0 100
0 100
Figure 51. Output Swing vs. Frequency
Figure 54. Output Swing vs. Frequency
VSY = 0.9V G=1 RL= NO LOAD CL = NO LOAD
VSY = 2.5V G=1 RL= NO LOAD CL = NO LOAD
VOLTAGE (500mV/DIV)
VOUT VIN
08056-052
VOLTAGE (1V/DIV)
VOUT VIN
TIME (200s/DIV)
TIME (200s/DIV)
Figure 52. No Phase Reversal
Figure 55. No Phase Reversal
Rev. 0 | Page 14 of 20
08056-055
08056-053
-150 20
VSY = 1.8V G = -100 RL= 10k CL= 50pF
-140
-150 20
VSY = 5V G = -100 RL= 10k CL = 50pF
ADA4051-2 THEORY OF OPERATION
The ADA4051-2 micropower chopper operational amplifier features a novel patent-pending technique that suppresses offset-related ripple in a chopper amplifier. It nulls out the amplifier's initial offset in the dc domain that otherwise becomes a ripple at the overall output, instead of filtering the ripple in the ac domain. Auto-zeroing and chopping are widely used for a high precision CMOS amplifier to achieve low offset, low offset drift, and no 1/f noise. Auto-zeroing and chopping both have pros and cons. Auto-zeroing gets more in-band noise due to aliasing introduced by sampling. Chopping has offset-related ripple, because it modulates the initial offset associated with the amplifier up to its chopping frequency. To accomplish the best noise vs. power trade-off, the chopping technique is the right approach to design a low offset amplifier. It is preferable to suppress the offset-related ripple in a chopper amplifier in the amplifier itself, which otherwise must be eliminated by an extra off-chip post filter. Figure 56 shows the block diagram design of the ADA4051-2 chopper amplifier, employing a local feedback loop called auto correction feedback (ACFB). The main signal path contains an input chopping switch network (CHOP1), a first transconductance amplifier (Gm1), an output chopping switch network (CHOP2), a second transconductance amplifier (Gm2), and a third transconductance amplifier (Gm3). CHOP1 and CHOP2 operate at 40 kHz of chopping frequency to modulate the initial offset and 1/f noise from Gm1 up to the chopping frequency. A fourth transconductance amplifier (Gm4) in the ACFB senses the modulated ripple at the output of CHOP2, caused by the initial offset voltage of Gm1. Then, the ripple is demodulated down to a dc domain through a third chopping switch network (CHOP3), operating with the same chopping clock as CHOP1 and CHOP2. Finally, a null transconductance amplifier (Gm5) tries to null out any dc component at the output of Gm1, which would otherwise appear in the overall output as ripple. A switched capacitor notch filter (NF) functions to selectively suppress the undesired offset-related ripple, without disturbing the desired input signal from the overall input. The desired input dc signal appears as a dc signal at CHOP2's output. Then, it is modulated up to the chopping frequency by CHOP3 and filtered out by the NF. Therefore, it does not create any feedback and does not disturb the desired input signal. The NF is synchronized with the chopping clock to perfectly filter out the modulated component. In the same manner, the offset of Gm5 is filtered out by the combination of CHOP3 and the NF, enabling accurate ripple sensing at the output of CHOP2. In parallel with the high dc gain path, a feedforward transconductance amplifier (Gm6) is added to bypass the phase shift introduced by the ACFB at the chopping frequency. The Gm6 is designed to have the same transconductance as the Gm1 to avoid the pole-zero doublets. Such design avoids any instability introduced by the ACFB in the overall feedback loop.
CHOP1 +IN -IN
Gm1
CHOP2
Gm2
C2 Gm3 OUT
C3
C1
Gm5 Gm6 (= Gm1)
NF CHOP3 Gm4
Figure 56. ADA4051-2 Chopper Amplifier Block Diagram
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08056-060
ADA4051-2
The voltage noise density is essentially flat from dc to the chopping frequency, whose level is just the thermal noise floor dominated by the Gm1, without receiving any addition due to the ACFB. Although the ACFB suppresses the ripple related to the chopping, there is a remaining voltage ripple. To further suppress the remaining ripple down to a desired level, it is recommended to have a post filter at the output of the amplifier. The remaining voltage ripple is composed of two ingredients. The first ripple's ingredient is due to the residual ripple associated with the initial offset of the Gm1. It is proportional to the magnitude of the initial offset and creates a spectrum at the chopping frequency (fCHOP). When the amplifier is configured as a unity gain buffer, this ripple has a typical value of 4.9 V rms and a maximum of 34.7 V rms. The second ripple's ingredient is due to the intermodulation between the high frequency input signal and the chopping frequency. It depends on the input frequency (fIN) and creates a spectrum at frequencies equal to the difference between the chopping frequency and the input frequency (fCHOP - fIN) and at their summation (fCHOP + fIN). The magnitude of the ripple for different input frequencies is shown in Figure 57.
500
MODULATED OUTPUT RIPPLE (V rms)
The design architecture of the ADA4051-2 specifically targets precision signal conditioning applications requiring accurate and stable performance from dc to 10 Hz bandwidth. In summary, the main features of the ADA4051-2 chopper amplifier are * * Considerable suppression of the offset-related ripple No affect on the desired input signal as long as its frequency is much lower than the chopping frequency shown in Figure 57 Achievement of low offset similar to a conventional chopper amplifier No introduction of excess noise
* *
The ADA4051-2 chopper amplifier provides rail-to-rail input range with 1.8 V to 5.5 V supply voltage range and 20 A supply current consumption over the -40C to +125C extended industrial temperature range. The gain bandwidth is 125 kHz as a unity gain stable amplifier up to 100 pF load capacitance.
INPUT VOLTAGE RANGE
The ADA4051-2 has internal ESD protection diodes. These diodes are connected between the inputs and each supply rail to protect the input MOSFETs against an electrical discharge event and are normally reversed-biased. This protection scheme allows voltages as high as approximately 0.3 V beyond the supplies (VSY 0.3 V) to be applied at the input of either terminal without causing permanent damage. If either input exceeds either supply rail by more than 0.3 V, these ESD diodes become forward-biased and large amounts of current begin to flow through them. Without current limiting, this excessive current causes permanent damage to the device. If the inputs are expected to be subject to overvoltage conditions, install a resistor in series with each input to limit the input current to 10 mA maximum.
400
300
200
100
0
1
2
3
4
5
6
7
8
9
10
08056-063
0
INPUT FREQUENCY (kHz)
Figure 57. ADA4051-2 Modulated Output Ripple vs. Input Frequency
The ADA4051-2 also has internal circuitry that protects the input stage from high differential voltages. This circuitry is composed of internal 1.33 k resistors in series with each input and backto-back diode-connected N-MOSFETs (with a typical VT of 0.7 V for VCM of 0 V) after these series resistors. Under normal negative feedback operating conditions, the ADA4051-2 amplifier corrects its output to ensure the two inputs are at the same voltage. However, if the device is configured as a comparator or is under some unusual operating condition, the input voltages may be forced to different potentials, which may cause excessive current to flow through the internal diode-connected NMOSFETs. Although the ADA4051-2 is a rail-to-rail input amplifier, take care to ensure that the potential difference between the inputs does not exceed VSY to avert permanent damage to the device.
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ADA4051-2
OUTPUT PHASE REVERSAL
Output phase reversal occurs in some amplifiers when the input common-mode voltage range is exceeded. As a common-mode voltage moves outside the common-mode range, the outputs of these amplifiers can suddenly jump in the opposite direction to the supply rail. This usually occurs when one of the internal stages of the amplifier no longer has sufficient bias voltage across it and subsequently turns off. The ADA4051-2 amplifier has been carefully designed to prevent any output phase reversal, provided both inputs are maintained approximately within 0.3 V above and below the supply voltages (VSY 0.3 V). If one or both inputs exceed the input voltage range but remain within the VSY 0.3 V range, an internal loop opens and the output remains in saturation mode, without phase reversal, until the input voltage is brought back to within the input voltage range limits as is shown in Figure 52 and Figure 55.
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ADA4051-2 OUTLINE DIMENSIONS
3.20 3.00 2.80
3.20 3.00 2.80 PIN 1
8
5
1
5.15 4.90 4.65
4
0.65 BSC 0.95 0.85 0.75 0.15 0.00 0.38 0.22 SEATING PLANE 1.10 MAX 8 0 0.80 0.60 0.40
0.23 0.08
COPLANARITY 0.10
COMPLIANT TO JEDEC STANDARDS MO-187-AA
Figure 58. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters
ORDERING GUIDE
Model ADA4051-2ARMZ 1 ADA4051-2ARMZ-R71 ADA4051-2ARMZ-RL1
1
Temperature Range -40C to +125C -40C to +125C -40C to +125C
Package Description 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP
Package Option RM-8 RM-8 RM-8
Branding A2M A2M A2M
Z = RoHS Compliant Part.
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ADA4051-2 NOTES
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ADA4051-2 NOTES
(c)2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D08056-0-7/09(0)
Rev. 0 | Page 20 of 20

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