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FEATURES Low Offset Voltage: 500 V Max Single Supply Operation: 2.7 V to 6 V Low Supply Current: 750 A/Amplifier Wide Bandwidth: 8 MHz Slew Rate: 5 V/ s Low Distortion No Phase Reversal Low Input Currents Unity Gain Stable APPLICATIONS Barcode Scanners Battery-Powered Instrumentation Multipole Filters Sensors Current Sensing ASIC Input or Output Amplifier Audio GENERAL DESCRIPTION
Precision CMOS Single Supply Rail-to-Rail Input/Output Wideband Operational Amplifiers AD8601/AD8602
FUNCTIONAL BLOCK DIAGRAMS 5-Lead SOT-23 (RT Suffix)
OUT A 1 V 2 5 V+
AD8601
4 IN
+IN 3
8-Lead SOIC (RM Suffix)
OUT A IN A IN A V 1 8
AD8602
4 5
V+ OUT B IN B +IN B
8-Lead SOIC (R Suffix)
OUT A 1 IN A 2 +IN A 3 V 4 8 V+
The AD8601 and AD8602 are single and dual rail-to-rail input and output single supply amplifiers featuring very low offset voltage and wide signal bandwidth. These amplifiers use a new, patented trimming technique that achieves superior performance without laser trimming. All are fully specified to operate from 3 V to 5 V single supply. The combination of low offsets, very low input bias currents, and high speed make these amplifiers useful in a wide variety of applications. Filters, integrators, diode amplifiers, shunt current sensors, and high impedance sensors all benefit from the combination of performance features. Audio and other ac applications benefit from the wide bandwidth and low distortion. For the most cost-sensitive applications the D grades offer this ac performance with lower dc precision at a lower price point. Applications for these amplifiers include audio amplification for portable devices, portable phone headsets, bar code scanners, portable instruments, and multipole filters.
AD8602
7 OUT B 6 IN B 5 +IN B
The ability to swing rail-to-rail at both the input and output enables designers to buffer CMOS ADCs, DACs, ASICs, and other wide output swing devices in single supply systems. The AD8601 and AD8602 are specified over the extended industrial (-40C to +125C) temperature range. The AD8601, single, is available in the tiny 5-lead SOT-23 package. The AD8602, dual, is available in 8-lead MSOP and narrow SOIC surface-mount packages. SOT and SOIC versions are available in tape and reel only.
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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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 2000
AD8601/AD8602-SPECIFICATIONS
ELECTRICAL CHARACTERISTICS (V = 3 V, V
S CM
= VS /2, TA = 25 C unless otherwise noted)
A Grade Min Typ Max 80 500 700 1,100 750 1,800 2,100 60 100 1,000 30 50 500 3 D Grade Min Typ Max 6,000 7,000 7,000 6,000 7,000 7,000 200 200 1,000 100 100 500 3 Unit V V V V V V pA pA pA pA pA pA V dB V/mV V/C V V mV mV mA dB A A V/s s MHz Degrees nV/Hz nV/Hz pA/Hz
Parameter INPUT CHARACTERISTICS Offset Voltage
Symbol VOS
Conditions 0 V VCM 1.3 V -40C TA +85C -40C TA +125C 0 V VCM 3 V1 -40C TA +85C -40C TA +125C -40C TA +85C -40C TA +125C
350
Input Bias Current
IB IOS
0.2
0.2
Input Offset Current
0.1 -40C TA +85C -40C TA +125C VCM = 0 V to 3 V VO = 0.5 V to 2.5 V RL = 2 k , VCM = 0 V 0 68 30 83 100 2
0.1
Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Offset Voltage Drift OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Output Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Voltage Noise Density Current Noise Density
CMRR AVO VOS /T VOH VOL IOUT ZOUT PSRR ISY
0 52 20
65 60 2
IL = 1.0 mA -40C TA +125C IL = 1.0 mA -40C TA +125C f = 1 MHz, AV = 1 VS = 2.7 V to 5.5 V VO = 0 V -40C TA +125C RL = 2 k To 0.01%
2.92 2.96 2.88 20 35 50 30 12 67 80 680
2.92 2.96 2.88 20 35 50 30 12 56 72 680
1,000 1,300
1,000 1,300
SR tS GBP o en en in
5.2 <0.5 8.2 50 33 18 0.05
5.2 <0.5 8.2 50 33 18 0.05
f = 1 kHz f = 10 kHz
NOTES 1 For VCM between 1.3 V and 1.8 V, V OS may exceed specified value. Specifications subject to change without notice.
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AD8601/AD8602 ELECTRICAL CHARACTERISTICS (V = 5.0 V, V
S CM
= VS /2, TA = 25 C unless otherwise noted)
A Grade Min Typ Max 80 0.2 500 1,300 60 100 1,000 30 50 500 5 D Grade Min Typ Max 6,000 7,000 200 200 1,000 100 100 500 5 Unit V V pA pA pA pA pA pA V dB V/mV V/C V V V mV mV mV mA dB A A V/s s kHz MHz Degrees nV/Hz nV/Hz pA/Hz
Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current
Symbol VOS IB IOS
Conditions 0 V VCM 5 V -40C TA +125C -40C TA +85C -40C TA +125C
0.2
Input Offset Current
0.1 -40C TA +85C -40C TA +125C VCM = 0 V to 5 V VO = 0.5 V to 4.5 V RL = 2 k, VCM = 0 V 0 74 30 89 100 2 IL = 1.0 mA IL = 10 mA -40C TA +125C IL = 1.0 mA IL = 10 mA -40C TA +125C f = 1 MHz, AV = 1 VS = 2.7 V to 5.5 V VO = 0 V -40C TA +125C RL = 2 k To 0.01% < 1% Distortion
0.1
Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Offset Voltage Drift OUTPUT CHARACTERISTICS Output Voltage High
CMRR AVO VOS /T VOH VOL IOUT ZOUT PSRR ISY
0 56 20
67 60 2
Output Voltage Low
Output Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Full Power Bandwidth Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Voltage Noise Density Current Noise Density
4.925 4.975 4.7 4.77 4.6 15 30 125 175 250 50 10 67 80 750
4.925 4.975 4.7 4.77 4.6 15 30 125 175 250 50 10 56 72 750
1,200 1,500
1,200 1,500
SR tS BWp GBP o en en in
6 < 1.0 360 8.4 55 33 18 0.05
6 < 1.0 360 8.4 55 33 18 0.05
f = 1 kHz f = 10 kHz f = 1 kHz
Specifications subject to change without notice.
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AD8601/AD8602
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 V Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GND to VS Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . 6 V Storage Temperature Range R, RM, RT Packages . . . . . . . . . . . . . . . . -65C to +150C Operating Temperature Range AD8601/AD8602 . . . . . . . . . . . . . . . . . . . -40C to +125C Junction Temperature Range R, RM, RT Packages . . . . . . . . . . . . . . . . -65C to +150C Lead Temperature Range (Soldering, 60 sec) . . . . . . . . 300C ESD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 kV HBM
*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 listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Package Type 5-Lead SOT-23 (RT) 8-Lead SOIC (R) 8-Lead MSOP (RM)
JA*
JC
Unit C/W C/W C/W
230 158 210
92 43 45
*JA is specified for worst-case conditions, i.e., JA is specified for device in socket for PDIP packages; JA is specified for device soldered onto a circuit board for surface mount packages.
ORDERING GUIDE
Model AD8601ART AD8601DRT AD8602AR AD8602DR AD8602ARM AD8602DRM
Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Package Description 5-Lead SOT-23 5-Lead SOT-23 8-Lead SOIC 8-Lead SOIC 8-Lead MSOP 8-Lead MSOP
Package Option RT-5 RT-5 SO-8 SO-8 RM-8 RM-8
Branding Information AAA AAD
ABA ABD
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD8601/AD8602 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
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Typical Performance Characteristics- AD8601/AD8602
3,000 VS = 3V TA = 25 C VCM = 0V TO 3V
QUANTITY - Amplifiers
60 VS = 5V TA = 25 C TO 85 C 50
2,500
QUANTITY - Amplifiers
2,000
40
1,500
30
1,000
20
500
10
0 1.0
0 0.8 0.6 0 0.4 0.2 0.2 0.4 0.6 INPUT OFFSET VOLTAGE - mV 0.8 1.0 0 1 2 3 4 5 6 TCVOS - V/ C 7 8 9 10
TPC 1. Input Offset Voltage Distribution
TPC 4. Input Offset Voltage Drift Distribution
3,000 VS = 5V TA = 25 C VCM = 0V TO 5V
1.5 1.0
VS = 3V TA = 25 C
INPUT OFFSET VOLTAGE - mV
2,500
QUANTITY - Amplifiers
0.5 0 0.5
2,000
1,500
1,000
1.0 1.5 2.0
500
0 1.0
0.8
0.6
0 0.4 0.2 0.2 0.4 0.6 INPUT OFFSET VOLTAGE - mV
0.8
1.0
0
0.5
1.0 1.5 2.0 COMMON-MODE VOLTAGE - V
2.5
3.0
TPC 2. Input Offset Voltage Distribution
TPC 5. Input Offset Voltage vs. Common-Mode Voltage
60 VS = 3V TA = 25 C TO 85 C
1.5 1.0
INPUT OFFSET VOLTAGE - mV
VS = 5V TA = 25 C
50
QUANTITY - Amplifiers
0.5 0 0.5
40
30
20
1.0 1.5 2.0
10
0 0 1 2 3 4 5 6 TCVOS - V/ C 7 8 9 10
0
1
2 3 COMMON-MODE VOLTAGE - V
4
5
TPC 3. Input Offset Voltage Drift Distribution
TPC 6. Input Offset Voltage vs. Common-Mode Voltage
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AD8601/AD8602
300 VS = 3V 250
INPUT OFFSET CURRENT - pA
30 VS = 3V 25
INPUT BIAS CURRENT - pA
200
20
150
15
100
10
50
5
0
40
25
10
5
20 35 50 65 TEMPERATURE - C
80
95
110
125
0
40
25
10
5
20 35 50 65 TEMPERATURE - C
80
95
110
125
TPC 7. Input Bias Current vs. Temperature
TPC 10. Input Offset Current vs. Temperature
300 VS = 5V 250
INPUT OFFSET CURRENT - pA INPUT BIAS CURRENT - pA
30 VS = 5V 25
200
20
150
15
100
10
50
5
0
40
25
10
5
20 35 50 65 TEMPERATURE - C
80
95
110
125
0
40
25
10
5
20 35 50 65 TEMPERATURE - C
80
95
110
125
TPC 8. Input Bias Current vs. Temperature
TPC 11. Input Offset Current vs. Temperature
5 VS = 5V TA = 25 C
INPUT BIAS CURRENT - pA
10k VS = 2.7V TA = 25 C 1k
4
3
OUTPUT VOLTAGE - mV
100 SOURCE SINK 10
2
1
1
0 0 0.5 1.0 2.0 2.5 3.0 3.5 4.0 1.5 COMMON-MODE VOLTAGE - V 4.5 5.0
0.1 0.001
0.01
0.1 1 LOAD CURRENT - mA
10
100
TPC 9. Input Bias Current vs. Common-Mode Voltage
TPC 12. Output Voltage to Supply Rail vs. Load Current
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REV. 0
AD8601/AD8602
10k VS = 5V TA = 25 C 1k 35 VS = 2.7V 30
OUTPUT VOLTAGE - mV
OUTPUT VOLTAGE - mV
25 VOL @ 1mA LOAD 20 15 10
SOURCE 100 SINK 10
1 5 0.1 0.001
0.01
0.1 1 LOAD CURRENT - mA
10
100
0
40
25
10
5
20 35 50 65 TEMPERATURE - C
80
95
110
125
TPC 13. Output Voltage to Supply Rail vs. Load Current
TPC 16. Output Voltage Swing vs. Temperature
5.1 VS = 5V 5.0
OUTPUT VOLTAGE - V
OUTPUT VOLTAGE - V
2.67 VS = 2.7V 2.66 VOH @ 1mA LOAD
4.9
2.65 VOH @ 1mA LOAD 2.64
4.8 VOH @ 10mA LOAD 4.7
4.6
2.63
4.5
40
25
10
5
20 35 50 65 TEMPERATURE - C
80
95
110
125
2.62
40
25
10
5
20 35 50 65 TEMPERATURE - C
80
95
110
125
TPC 14. Output Voltage Swing vs. Temperature
TPC 17. Output Voltage Swing vs. Temperature
250 VS = 5V 200 80 60 VOL @ 10mA LOAD 45 90 135 180 VS = 3V RL = NO LOAD TA = 25 C
OUTPUT VOLTAGE - mV
GAIN - dB
150
40 20 0
100
50 VOL @ 1mA LOAD 0 40 25 10 5 20 35 50 65 TEMPERATURE - C 80 95 110 125
1k
10k
100k 1M FREQUENCY - Hz
10M
100M
TPC 15. Output Voltage Swing vs. Temperature
TPC 18. Open-Loop Gain and Phase vs. Frequency
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PHASE SHIFT - Degrees
AD8601/AD8602
3.0
80 60
VS = 5V RL = NO LOAD TA = 25 C
2.5
PHASE SHIFT - Degrees
45 90 135 180
OUTPUT SWING - V p-p
2.0
GAIN - dB
40 20 0
VS = 2.7V VIN = 2.6V p-p RL = 2k TA = 25 C AV = 1
1.5
1.0
0.5
1k
10k
100k 1M FREQUENCY - Hz
10M
100M
0 1k
10k
100k FREQUENCY - Hz
1M
10M
TPC 19. Open-Loop Gain and Phase vs. Frequency
TPC 22. Closed-Loop Output Voltage Swing vs. Frequency
6
VS = 3V TA = 25 C 40
AV = 100
OUTPUT SWING - V p-p
5 VS = 5V VIN = 4.9V p-p RL = 2k TA = 25 C AV = 1
CLOSED-LOOP GAIN - dB
20
AV = 10
4
3
0
AV = 1
2
1
1k
10k
100k 1M FREQUENCY - Hz
10M
100M
0 1k
10k
100k FREQUENCY - Hz
1M
10M
TPC 20. Closed-Loop Gain vs. Frequency
TPC 23. Closed-Loop Output Voltage Swing vs. Frequency
200 VS = 5V TA = 25 C 40 180 AV = 100 160 VS = 3V TA = 25 C
CLOSED-LOOP GAIN - dB
OUTPUT IMPEDANCE -
140 AV = 100 120 100 AV = 10 80 AV = 1 60 40 20
20
AV = 10
0
AV = 1
1k
10k
100k 1M FREQUENCY - Hz
10M
100M
0 100
1k
10k 100k FREQUENCY - Hz
1M
10M
TPC 21. Closed-Loop Gain vs. Frequency
TPC 24. Output Impedance vs. Frequency
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AD8601/AD8602
200 180 160 VS = 5V TA = 25 C 160 140 VS = 5V TA = 25 C
POWER SUPPLY REJECTION - dB
120 100 80 60 40 20 0 20
OUTPUT IMPEDANCE -
140 120 AV = 100 100 AV = 10 80 AV = 1 60 40 20 0 100 1k 10k 100k FREQUENCY - Hz 1M 10M
40 100
1k
10k 100k FREQUENCY - Hz
1M
10M
TPC 25. Output Impedance vs. Frequency
TPC 28. Power Supply Rejection Ratio vs. Frequency
160 VS = 3V 140 T = 25 C A
COMMON-MODE REJECTION - dB
70 60
SMALL SIGNAL OVERSHOOT - %
120 100 80 60 40 20 0 20 40 1k 10k 100k FREQUENCY - Hz 1M 10M 20M
VS = 2.7V RL = TA = 25 C
50 OS 40 30 +OS 20
10 0 10
100 CAPACITANCE - pF
1k
TPC 26. Common-Mode Rejection Ratio vs. Frequency
TPC 29. Small Signal Overshoot vs. Load Capacitance
160 140
COMMON-MODE REJECTION - dB
70
VS = 5V TA = 25 C
60
SMALL SIGNAL OVERSHOOT - %
120 100 80 60 40 20 0 20 40 1k 10k 100k FREQUENCY - Hz 1M 10M 20M
VS = 5V RL = TA = 25 C
50
40 30 20 OS 10 +OS 0 10 100 CAPACITANCE - pF 1k
TPC 27. Common-Mode Rejection Ratio vs. Frequency
TPC 30. Small Signal Overshoot vs. Load Capacitance
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AD8601/AD8602
1.2
SUPPLY CURRENT PER AMPLIFIER - mA
0.1
VS = 5V 1.0
VS = 5V TA = 25 C G = 10
RL = 600 RL = 2k RL = 10k RL = 600 G=1 RL = 2k RL = 10k
0.8
THD + N - %
0.01
0.6
0.4
0.001
0.2
0
40
25
10
5
20 35 50 65 TEMPERATURE - C
80
95
110
125
0.0001
20
100
1k FREQUENCY - Hz
10k
20k
TPC 31. Supply Current per Amplifier vs. Temperature
TPC 34. Total Harmonic Distortion + Noise vs. Frequency
1.0
64
VS = 3V
SUPPLY CURRENT PER AMPLIFIER - mA
0.8
VOLTAGE NOISE DENSITY - nV/ Hz
56 48 40 32 24 16 8
VS = 2.7V TA = 25 C
0.6
0.4
0.2
0
40
25
10
5
20 35 50 65 TEMPERATURE - C
80
95
110
125
0
0
5
10 15 FREQUENCY - kHz
20
25
TPC 32. Supply Current per Amplifier vs. Temperature
TPC 35. Voltage Noise Density vs. Frequency
0.8
208 182 156 130 104 78 52 26 0 VS = 2.7V TA = 25 C
SUPPLY CURRENT PER AMPLIFIER - mA
0.6 0.5 0.4 0.3 0.2 0.1 0
0
1
2 3 4 SUPPLY VOLTAGE - V
5
6
VOLTAGE NOISE DENSITY - nV/ Hz
0.7
0
0.5
1.0 1. FREQUENCY - 5 kHz
2.0
2.5
TPC 33. Supply Current per Amplifier vs. Supply Voltage
TPC 36. Voltage Noise Density vs. Frequency
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AD8601/AD8602
208 182 156 130 104 78 52 26 0 VS = 5V TA = 25 C VS = 5V TA = 25 C VOLTAGE NOISE DENSITY - nV/ Hz
0
0.5
1.0 1.5 FREQUENCY - kHz
2.0
2.5 TIME - 1s/DIV
TPC 37. Voltage Noise Density vs. Frequency
VOLTAGE - 2.5 V/DIV
TPC 40. 0.1 Hz to 10 Hz Input Voltage Noise
64 56 48 40 32 24 16 8 0 VS = 5V TA = 25 C
VOLTAGE NOISE DENSITY - nV/ Hz
VS = 5V RL = 10k CL = 100pF TA = 25 C
0
5
10 15 FREQUENCY - kHz
20
25
VOLTAGE - 50mV/DIV
TIME - 200ns/DIV
TPC 38. Voltage Noise Density vs. Frequency
TPC 41. Small Signal Transient Response
VS = 2.7V TA = 25 C
VS = 5V TA = 25 C
VOLTAGE - 2.5 V/DIV
VOLTAGE - 2.5 V/DIV
TIME - 1s/DIV
TIME - 1s/DIV
TPC 39. 0.1 Hz to 10 Hz Input Voltage Noise
TPC 42. Small Signal Transient Response
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AD8601/AD8602
VS = 5V RL = 10k CL = 200pF AV = 1 TA = 25 C
VS = 5V RL = 10k AV = 1 TA = 25 C
VOLTAGE - 1.0V/DIV
VIN
VOLTAGE - 1V/DIV
VOUT
TIME - 400ns/DIV
TIME - 2.0 s/DIV
TPC 43. Large Signal Transient Response
TPC 46. No Phase Reversal
VOLTAGE - 500mV/DIV
VS = 2.7V RL = 10k CL = 200pF AV = 1 TA = 25 C
VOLTAGE - V
VS = 5V RL = 10k VO = 2V p-p TA = 25 C VIN
+0.1% ERROR
VOUT 0.1% ERROR
VIN TRACE - 0.5V/DIV VOUT TRACE - 10mV/DIV TIME - 100ns/DIV
TIME - 400ns/DIV
TPC 44. Large Signal Transient Response
TPC 47. Settling Time
2.0 VS = 2.7V RL = 10k AV = 1 TA = 25 C 1.5 1.0 VS = 2.7V TA = 25 C 0.1% 0.01%
OUTPUT SWING - V
VOLTAGE - 1V/DIV
VIN VOUT
0.5 0 0.5 0.1% 1.0 1.5 2.0 300 0.01%
350
TIME - 2.0 s/DIV
400 450 500 SETTLING TIME - ns
550
600
TPC 45. No Phase Reversal
TPC 48. Output Swing vs. Settling Time
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AD8601/AD8602
5 4 3 VS = 5V TA = 25 C
OUTPUT SWING - V
2 1 0.1% 0 1 2 3 4 5 0 200 400 600 SETTLING TIME - ns 800 1,000 0.1% 0.01% 0.01%
for single supply and low voltage applications. This rail-to-rail input range is achieved by using two input differential pairs, one NMOS and one PMOS, placed in parallel. The NMOS pair is active at the upper end of the common-mode voltage range, and the PMOS pair is active at the lower end of the common-mode range. The NMOS and PMOS input stage are separately trimmed using DigiTrim to minimize the offset voltage in both differential pairs. Both NMOS and PMOS input differential pairs are active in a 500 mV transition region, when the input common-mode voltage is between approximately 1.5 V and 1 V below the positive supply voltage. Input offset voltage will shift slightly in this transition region, as shown in Figures 5 and 6. Common-mode rejection ratio will also be slightly lower when the input common-mode voltage is within this transition band. Compared to the Burr Brown OPA2340 rail-to-rail input amplifier, shown in Figure 1, the AD860x, shown in Figure 2, exhibits lower offset voltage shift across the entire input common-mode range, including the transition region.
TPC 49. Output Swing vs. Settling Time
THEORY OF OPERATION
The AD8601/AD8602 family of amplifiers are rail-to-rail input and output precision CMOS amplifiers specified from 2.7 V to 5.0 V of power supply voltage. These amplifiers use Analog Devices' proprietary technology called DigiTrimTM to achieve a higher degree of precision than available from most CMOS amplifiers. DigiTrim technology is a method of trimming the offset voltage of the amplifier after it has already been assembled. The advantage in post-package trimming lies in the fact that it corrects any offset voltages due to the mechanical stresses of assembly. This technology is scalable and utilized with every package option, including SOT23-5, providing lower offset voltages than previously achieved in these small packages. The DigiTrim process is done at the factory and does not add additional pins to the amplifier. All AD860x amplifiers are available in standard op amp pinouts, making DigiTrim completely transparent to the user. The AD860x can be used in any precision op amp application. The input stage of the amplifier is a true rail-to-rail architecture, allowing the input common-mode voltage range of the op amp to extend to both positive and negative supply rails. The voltage swing of the output stage is also rail-to-rail and is achieved by using an NMOS and PMOS transistor pair connected in a common-source configuration. The maximum output voltage swing is proportional to the output current, and larger currents will limit how close the output voltage can get to the supply rail. This is a characteristic of all rail-to-rail output amplifiers. With 1 mA of output current, the output voltage can reach within 20 mV of the positive rail and 15 mV of the negative rail. The open-loop gain of the AD860x is 100 dB, typical, with a load of 2 k. Because of the rail-to-rail output configuration, the gain of the output stage, and thus the open-loop gain of the amplifier, is dependent on the load resistance. Open-loop gain will decrease with smaller load resistances. Again, this is a characteristic inherent to all rail-to-rail output amplifiers.
Rail-to-Rail Input Stage
0.7
0.4 0.1 VOS - mV
0.2 0.5 0.8
1.1 1.4
0
1
2 VCM - V
3
4
5
Figure 1. Burr Brown OPA2340UR Input Offset Voltage vs. Common-Mode Voltage, 24 SOIC Units @ 25C
0.7 0.4 0.1
VOS - mV
0.2 0.5
0.8 1.1 1.4
The input common-mode voltage range of the AD860x extends to both positive and negative supply voltages. This maximizes the usable voltage range of the amplifier, an important feature
0
1
2 VCM - V
3
4
5
Figure 2. AD8602AR Input Offset Voltage vs. Common-Mode Voltage, 300 SOIC Units @ 25C
DigiTrim is a trademark of Analog Devices.
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AD8601/AD8602
Input Overvoltage Protection
As with any semiconductor device, if a condition could exist for the input voltage to exceed the power supply, the device's input overvoltage characteristic must be considered. Excess input voltage will energize internal PN junctions in the AD860x, allowing current to flow from the input to the supplies. This input current will not damage the amplifier provided it is limited to 5 mA or less. This can be ensured by placing a resistor in series with the input. For example, if the input voltage could exceed the supply by 5 V, the series resistor should be at least (5 V/5 mA) = 1 k. With the input voltage within the supply rails, a minimal amount of current is drawn into the inputs which, in turn, causes a negligible voltage drop across the series resistor. Thus, adding the series resistor will not adversely affect circuit performance.
Overdrive Recovery
10pF (OPTIONAL)
4.7m
D1
VOUT 4.7V/ A
AD8601
Figure 3. Amplifier Photdiode Circuit
High- and Low-Side Precision Current Monitoring
Overdrive recovery is defined as the time it takes the output of an amplifier to come off the supply rail when recovering from an overload signal. This is tested by placing the amplifier in a closed-loop gain of 10 with an input square wave of 2 V peak-to-peak while the amplifier is powered from either 5 V or 3 V. The AD860x has excellent recovery time from overload conditions. The output recovers from the positive supply rail within 200 ns at all supply voltages. Recovery from the negative rail is within 500 ns at 5 V supply, decreasing to within 350 ns when the device is powered from 2.7 V.
Power-On Time
Because of its low input bias current and low offset voltage, the AD860x can be used for precision current monitoring. The true rail-to-rail input feature of the AD860x allows the amplifier to monitor current on either high-side or low-side. Using both amplifiers in an AD8602 provides a simple method for monitoring both current supply and return paths for load or fault detection. Figure 4 and 54 demonstrate both circuits.
3V R2 2.49k MONITOR OUTPUT Q1 2N3905 3V
R1 100 RSENSE 0.1
1/2 AD8602
RETURN TO GROUND
Power-on time is important in portable applications, where the supply voltage to the amplifier may be toggled to shut down the device to improve battery life. Fast power-up behavior ensures the output of the amplifier will quickly settle to its final voltage, thus improving the power-up speed of the entire system. Once the supply voltage reaches a minimum of 2.5 V, the AD860x will settle to a valid output within 1 s. This turn-on response time is faster than many other precision amplifiers, which can take tens or hundreds of microseconds for their output to settle.
Using the AD8602 in High Source Impedance Applications
Figure 4. A Low-Side Current Monitor
RSENSE 0.1 3V 3V 0.1 F R1 100 IL V+
1/2 AD8602
The CMOS rail-to-rail input structure of the AD860x allows these amplifiers to have very low input bias currents, typically 0.2 pA. This allows the AD860x to be used in any application that has a high source impedance or must use large value resistances around the amplifier. For example, the photodiode amplifier circuit shown in Figure 3 requires a low input bias current op amp to reduce output voltage error. The AD8601 minimizes offset errors due to its low input bias current and low offset voltage. The current through the photodiode is proportional to the incident light power on its surface. The 4.7 M resistor converts this current into a voltage, with the output of the AD8601 increasing at 4.7 V/A. The feedback capacitor reduces excess noise at higher frequencies by limiting the bandwidth of the circuit to:
BW = 1 2(4.7 M)C F
(1)
Q1 2N3904 MONITOR OUTPUT
R2 2.49k
Figure 5. A High-Side Current Monitor
Voltage drop is created across the 0.1 resistor that is proportional to the load current. This voltage appears at the inverting input of the amplifier due to the feedback correction around the op amp. This creates a current through R1 which, in turn, pulls current through R2. For the low side monitor, the monitor output voltage is given by:
R Monitor Output = R2 x SENSE x I L R1
(2)
Using a 10 pF feedback capacitor limits the bandwidth to approximately 3.3 kHz.
For the high-side monitor, the monitor output voltage is:
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REV. 0
AD8601/AD8602
R Monitor Output = V + ( -R2) x SENSE x I L R1
PC100 Compliance for Computer Audio Applications (3)
Using the components shown, the monitor output transfer function is 2.5 V/A.
Using the AD8601 in Single Supply Mixed-Signal Applications
Single supply mixed-signal applications requiring 10 or more bits of resolution demand both a minimum of distortion and a maximum range of voltage swing to optimize performance. To ensure the A/D or D/A converters achieve their best performance an amplifier often must be used for buffering or signal conditioning. The 750 V maximum offset voltage of the AD8601 allows the amplifier to be used in 12-bit applications powered from a 3 V single supply, and its rail-to-rail input and output ensure no signal clipping. Figure 6 shows the AD8601 used as a input buffer amplifier to the AD7476, a 12-bit 1 MHz A/D converter. As with most A/D converters, total harmonic distortion (THD) increases with higher source impedances. By using the AD8601 in a buffer configuration, the low output impedance of the amplifier minimizes THD while the high input impedance and low bias current of the op amp minimizes errors due to source impedance. The 8 MHz gain-bandwidth product of the AD8601 ensures no signal attenuation up to 500 kHz, which is the maximum Nyquist frequency for the AD7476.
3V 680nF 1F TANT REF193 0.1 F 10 F 5V SUPPLY 0.1 F
Because of its low distortion and rail-to-rail input and output, the AD860x is an excellent choice for low cost, single supply audio applications, ranging from microphone amplification to line output buffering. TPC 34 shows the total harmonic distortion plus noise (THD + N) figures for the AD860x. In unity gain, the amplifier has a typical THD + N of 0.004%, or -86 dB, even with a load resistance of 600 . This is compliant with the PC100 specification requirements for audio in both portable and desktop computers. Figure 8 shows how an AD8602 can be interfaced with an AC'97 codec to drive the line output. Here, the AD8602 is used as a unity-gain buffer from the left and right outputs of the AC'97 CODEC. The 100 F output coupling capacitors block dc current and the 20 series resistors protect the amplifier from short-circuits at the jack.
+5V VDD 2 VDD 28 U1-A LEFTOUT 35 3 4 +5V 8 1 C1 100 F R2 2k R4 20
AD1881 (AC97)
RIGHTOUT 36 VSS 5 U1-B 6 7 C2 100 F R3 2k R5 20
4 RS 3
5 1 2
VDD VIN GND
SCLK SDATA CS C/ P
NOTE: ADDITIONAL PINS OMITTED FOR CLARITY
U1 = AD8602D
AD8601
VIN
Figure 8. A PC100 Compliant Line Output Amplifier
SPICE Model
AD7476/AD7477
SERIAL INTERFACE
Figure 6. A Complete 3 V 12-Bit 1 MHz A/D Conversion System
Figure 7 demonstrates how the AD8601 can be used as an output buffer for the DAC for driving heavy resistive loads. The AD5320 is a 12-bit D/A converter that can be used with clock frequencies up to 30 MHz and signal frequencies up to 930 kHz. The rail-torail output of the AD8601 allows it to swing within 100 mV of the positive supply rail while sourcing 1 mA of current. The total current drawn from the circuit is less than 1 mA, or 3 mW from a 3 V single supply.
3V
The SPICE macro-model for the AD860x amplifier is available and can be downloaded from the Analog Devices website at http://www.analog.com. The model will accurately simulate a number of both dc and ac parameters, including open-loop gain, bandwidth, phase margin, input voltage range, output voltage swing versus output current, slew rate, input voltage noise, CMRR, PSRR, and supply current versus supply voltage. The model is optimized for performance at 27C. Although it will function at different temperatures, it may lose accuracy with respect to the actual behavior of the AD860x.
1F 4 3-WIRE SERIAL INTERFACE 5 6 4 5 1 VOUT 0V TO 3.0V RL
AD5320
2
1
3 2
AD8601
Figure 7. Using the AD8601 as a DAC Output Buffer to Drive Heavy Loads
The AD8601, AD7476, and AD5320 are all available in spacesaving SOT-23 packages.
REV. 0
-15-
AD8601/AD8602
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
5-Lead SOT-23 (RT Suffix)
0.1220 (3.100) 0.1063 (2.700)
8-Lead SOIC (RM Suffix)
0.122 (3.10) 0.114 (2.90)
0.0709 (1.800) 0.0590 (1.500) PIN 1
5 1 2
4 3
8
5
0.1181 (3.000) 0.0984 (2.500)
0.122 (3.10) 0.114 (2.90)
1 4
0.199 (5.05) 0.187 (4.75)
0.0374 (0.950) REF 0.0748 (1.900) REF 0.0512 (1.300) 0.0354 (0.900) 0.0059 (0.150) 0.0000 (0.000) 0.0571 (1.450) 0.0354 (0.900) 0.0197 (0.500) 0.0118 (0.300) SEATING PLANE 10 0
PIN 1 0.0256 (0.65) BSC
0.0079 (0.200) 0.0035 (0.090)
0.120 (3.05) 0.112 (2.84) 0.006 (0.15) 0.002 (0.05) 0.018 (0.46) SEATING 0.008 (0.20) PLANE 0.043 (1.09) 0.037 (0.94) 0.011 (0.28) 0.003 (0.08)
0.120 (3.05) 0.112 (2.84) 33 27
0.0236 (0.600) 0.0039 (0.100)
0.028 (0.71) 0.016 (0.41)
8-Lead SOIC (SO Suffix)
0.1968 (5.00) 0.1890 (4.80)
8 5 4
0.1574 (4.00) 0.1497 (3.80) 1
0.2440 (6.20) 0.2284 (5.80)
PIN 1 0.0098 (0.25) 0.0040 (0.10)
0.0688 (1.75) 0.0532 (1.35)
0.0196 (0.50) x 45 0.0099 (0.25)
0.0500 0.0192 (0.49) SEATING (1.27) PLANE BSC 0.0138 (0.35)
0.0098 (0.25) 0.0075 (0.19)
8 0
0.0500 (1.27) 0.0160 (0.41)
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REV. 0
PRINTED IN U.S.A.
C3684-2.5-4/00 01525

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