ANALOG DEVICES AD8610, AD8620 Service Manual

Low Input Bias Current, Wide Bandwidth
JFET Operational Amplifier
AD8610/AD8620
FEATURES Low Noise 6 nV/
Hz
Low Offset Voltage: 100 V Max Low Input Bias Current 10 pA Max Fast Settling: 600 ns to 0.01% Low Distortion Unity Gain Stable No Phase Reversal Dual-Supply Operation: 5 V to 13 V
APPLICATIONS Photodiode Amplifier ATE Instrumentation Sensors and Controls High Performance Filters Fast Precision Integrators High Performance Audio

GENERAL DESCRIPTION

The AD8610/AD8620 is a very high precision JFET input amplifier featuring ultralow offset voltage and drift, very low input voltage and current noise, very low input bias current, and wide bandwidth. Unlike many JFET amplifiers, the AD8610/AD8620 input bias current is low over the entire operating temperature range. The AD8610/AD8620 is stable with capacitive loads of over 1000 pF in noninverting unity gain; much larger capacitive loads can be driven easily at higher noise gains. The AD8610/AD8620 swings to within 1.2 V of the supplies even with a 1 kload, maximizing dynamic range even with limited supply voltages. Outputs slew at 50 V/µs in either inverting or noninverting gain configurations, and settle to 0.01% accuracy in less than 600 ns. Combined with the high input impedance, great precision, and very high output drive, the

FUNCTIONAL BLOCK DIAGRAMS

8-Lead MSOP and SOIC (RM-8 and R-8 Suffixes)
1
NULL
ININ
V
NC = NO CONNECT
8
AD8610
45
NC V OUT NULL
8-Lead SOIC
(R-8 Suffix)
1
OUTA
INAINA
V
8
AD8620
45
V OUTB
INBINB
AD8610/AD8620 is an ideal amplifier for driving high performance A/D inputs and buffering D/A converter outputs.
Applications for the AD8610/AD8620 include electronic instru­ments; ATE amplification, buffering, and integrator circuits; CAT/MRI/ultrasound medical instrumentation; instrumentation quality photodiode amplification; fast precision filters (including PLL filters); and high quality audio.
The AD8610/AD8620 is fully specified over the extended industrial (–40°C to +125°C) temperature range. The AD8610 is available in the narrow 8-lead SOIC and the tiny MSOP8 surface-mount packages. The AD8620 is available in the narrow 8-lead SOIC package. MSOP8 packaged devices are available only in tape and reel.
REV. D
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. 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: 781/326-8703 © 2004 Analog Devices, Inc. All rights reserved.
AD8610/AD8620–SPECIFICATIONS
(@ VS = 5.0 V, VCM = 0 V, TA = 25C, unless otherwise noted.)
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage (AD8610B) V
Offset Voltage (AD8620B) V
Offset Voltage (AD8610A/AD8620A) V
Input Bias Current I
Input Offset Current I
B
OS
OS
OS
OS
–40°C < T
–40°C < T
+25°C < T –40°C < T
–40°C < T –40°C < T
–40°C < T –40°C < T
< +125°C80200 µV
A
< +125°C80300 µV
A
< 125°C90350 µV
A
< +125°C 150 850 µV
A
–10 +2 +10 pA
< +85°C –250 +130 +250 pA
A
< +125°C –2.5 +1.5 +2.5 nA
A
–10 +1 +10 pA
< +85°C –75 +20 +75 pA
A
< +125°C –150 +40 +150 pA
A
45 100 µV
45 150 µV
85 250 µV
Input Voltage Range –2 +3 V Common-Mode Rejection Ratio CMRR V Large Signal Voltage Gain A Offset Voltage Drift (AD8610B) ∆V Offset Voltage Drift (AD8620B) ∆V
VO
/T –40°C < TA < +125°C 0.5 1 µV/°C
OS
/T –40°C < TA < +125°C 0.5 1.5 µV/°C
OS
= –2.5 V to +1.5 V 90 95 dB
CM
RL = 1 k, VO = –3 V to +3 V 100 180 V/mV
Offset Voltage Drift (AD8610A/AD8620A) ∆VOS/T –40°C < TA < +125°C 0.8 3.5 µV/°C
OUTPUT CHARACTERISTICS
Output Voltage High V Output Voltage Low V Output Current I
OH
OL
OUT
RL = 1 k, –40°C < TA < +125°C 3.8 4 V RL = 1 k, –40°C < TA < +125°C–4–3.8 V V
> ±2 V ± 30 mA
OUT
POWER SUPPLY
Power Supply Rejection Ratio PSRR VS = ±5 V to ±13 V 100 110 dB Supply Current/Amplifier I
SY
VO = 0 V 2.5 3.0 mA –40°C < TA < +125°C 3.0 3.5 mA
DYNAMIC PERFORMANCE
Slew Rate SR RL = 2 k 40 50 V/µs Gain Bandwidth Product GBP 25 MHz Settling Time t
S
AV = +1, 4 V Step, to 0.01% 350 ns
NOISE PERFORMANCE
Voltage Noise en p-p 0.1 Hz to 10 Hz 1.8 µV p-p Voltage Noise Density e Current Noise Density i Input Capacitance C
n
n
IN
f = 1 kHz 6 nV/√Hz f = 1 kHz 5 fA/√Hz
Differential 8pF Common-Mode 15 pF
Channel Separation C
S
f = 10 kHz 137 dB f = 300 kHz 120 dB
Specifications subject to change without notice.
REV. D–2–
AD8610/AD8620

ELECTRICAL SPECIFICATIONS

(@ VS = 13 V, VCM = 0 V, TA = 25C, unless otherwise noted.)
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage (AD8610B) V
OS
45 100 µV
–40°C < TA < +125°C80200 µV
Offset Voltage (AD8620B) V
Offset Voltage (AD8610A/AD8620A) V
Input Bias Current I
OS
–40°C < T
OS
+25°C < T –40°C < T
B
–40°C < T
< +125°C80300 µV
A
< 125°C90350 µV
A
< +125°C 150 850 µV
A
–10 +3 +10 pA
< +85°C –250 +130 +250 pA
A
45 150 µV
85 250 µV
–40°C < TA < +125°C –3.5 +3.5 nA
Input Offset Current I
OS
–40°C < T
< +85°C –75 +20 +75 pA
A
–10 +1.5 +10 pA
–40°C < TA < +125°C –150 +40 +150 pA
Input Voltage Range –10.5 +10.5 V Common-Mode Rejection Ratio CMRR V Large Signal Voltage Gain A Offset Voltage Drift (AD8610B) ∆V Offset Voltage Drift (AD8620B) ∆V
VO
/T –40°C < TA < +125°C 0.5 1 µV/°C
OS
/T –40°C < TA < +125°C 0.5 1.5 µV/°C
OS
= –10 V to +10 V 90 110 dB
CM
RL = 1 k, VO = –10 V to +10 V 100 200 V/mV
Offset Voltage Drift (AD8610A/AD8620A) ∆VOS/T –40°C < TA < +125°C 0.8 3.5 µV/°C
OUTPUT CHARACTERISTICS
Output Voltage High V Output Voltage Low V Output Current I Short Circuit Current I
OH
OL
OUT
SC
RL = 1 k, –40°C < TA < +125°C +11.75 +11.84 V RL = 1 k, –40°C < TA < +125°C –11.84 –11.75 V V
> 10 V ±45 mA
OUT
±65 mA
POWER SUPPLY
Power Supply Rejection Ratio PSRR VS = ±5 V to ±13 V 100 110 dB Supply Current/Amplifier I
SY
VO = 0 V 3.0 3.5 mA –40°C < TA < +125°C 3.5 4.0 mA
DYNAMIC PERFORMANCE
Slew Rate SR RL = 2 k 40 60 V/µs Gain Bandwidth Product GBP 25 MHz Settling Time t
S
AV = 1, 10 V Step, to 0.01% 600 ns
NOISE PERFORMANCE
Voltage Noise en p-p 0.1 Hz to 10 Hz 1.8 µV p-p Voltage Noise Density e Current Noise Density i Input Capacitance C
n
n
IN
f = 1 kHz 6 nV/√Hz f = 1 kHz 5 fA/√Hz
Differential 8pF Common-Mode 15 pF
Channel Separation C
S
f = 10 kHz 137 dB f = 300 kHz 120 dB
Specifications subject to change without notice.
REV. D
–3–
AD8610/AD8620

ABSOLUTE MAXIMUM RATINGS*

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.3 V
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
S––
to V
S+
Differential Input Voltage . . . . . . . . . . . . . . . ± Supply Voltage
Output Short-Circuit Duration to GND . . . . . . . . . . Indefinite
Storage Temperature Range
R, RM Packages . . . . . . . . . . . . . . . . . . . . .–65°C to +150°C
Operating Temperature Range
AD8610/AD8620 . . . . . . . . . . . . . . . . . . . .–40°C to +125°C
Junction Temperature Range
R, RM Packages . . . . . . . . . . . . . . . . . . . . .–65°C to +150°C
Lead Temperature Range (Soldering, 10 sec) . . . . . . . . 300°C
*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.

ORDERING GUIDE

Temperature Package Package
Model Range Description Option Branding
AD8610AR –40°C to +125°C 8-Lead SOIC RN-8 AD8610AR-REEL –40°C to +125°C 8-Lead SOIC RN-8 AD8610AR-REEL7 –40°C to +125°C 8-Lead SOIC RN-8 AD8610ARM-REEL –40°C to +125°C 8-Lead MSOP RM-8 B0A AD8610ARM-R2 –40°C to +125°C 8-Lead MSOP RM-8 B0A AD8610ARZ* –40°C to +125°C 8-Lead SOIC RN-8 AD8610ARZ-REEL* –40°C to +125°C 8-Lead SOIC RN-8 AD8610ARZ-REEL7* –40°C to +125°C 8-Lead SOIC RN-8 AD8610BR –40°C to +125°C 8-Lead SOIC RN-8 AD8610BR-REEL –40°C to +125°C 8-Lead SOIC RN-8 AD8610BR-REEL7 –40°C to +125°C 8-Lead SOIC RN-8 AD8610BRZ* –40°C to +125°C 8-Lead SOIC RN-8 AD8610BRZ-REEL* –40°C to +125°C 8-Lead SOIC RN-8 AD8610BRZ-REEL7* –40°C to +125°C 8-Lead SOIC RN-8 AD8620AR –40°C to +125°C 8-Lead SOIC RN-8 AD8620AR-REEL –40°C to +125°C 8-Lead SOIC RN-8 AD8620AR-REEL7 –40°C to +125°C 8-Lead SOIC RN-8 AD8620BR –40°C to +125°C 8-Lead SOIC RN-8 AD8620BR-REEL –40°C to +125°C 8-Lead SOIC RN-8 AD8620BR-REEL7 –40°C to +125°C 8-Lead SOIC RN-8
Package Type JA*
JC
Unit
8-Lead MSOP (RM) 190 44 °C/W 8-Lead SOIC (RN) 158 43 °C/W
*θJA is specified for worst-case conditions; i.e., θ
soldered in circuit board for surface-mount packages.
is specified for a device
JA
*Pb-free part
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 AD8610/AD8620 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.
REV. D–4–
Typical Performance Characteristics–AD8610/AD8620
14
12
10
8
6
4
NUMBER OF AMPLIFIERS
2
0
150
250
50
INPUT OFFSET VOLTAGE – ␮V
VS = ⴞ13V
50 150
250
TPC 1. Input Offset Voltage at±13 V
600
400
200
0
–200
–400
INPUT OFFSET VOLTAGE – ␮V
–600
–40 25 85 125
TEMPERATURE – ⴗC
V
S
= ⴞ5V
600
VS = ⴞ13V
400
200
0
200
400
INPUT OFFSET VOLTAGE – V
600
40
25 85 125
TEMPERATURE – ⴗC
TPC 2. Input Offset Voltage vs. Temperature at±13 V (300 Amplifiers)
14
12
10
8
6
4
NUMBER OF AMPLIFIERS
2
0
00.2 0.6 1.0 1.4 1.8 2.2 2.6
VS = 5V OR ⴞ13V
TCVOS – V/ⴗC
18
16
14
12
10
8
6
4
NUMBER OF AMPLIFIERS
2
0
150
250
50
INPUT OFFSET VOLTAGE – ␮V
VS = ⴞ5V
50 150
250
TPC 3. Input Offset Voltage at±5 V
3.6
3.4
3.2
3.0
2.8
2.6
2.4
INPUT BIAS CURRENT – pA
2.2
2.0 10 5
COMMON-MODE VOLTAGE – V
0510
VS = ⴞ13V
TPC 4. Input Offset Voltage vs. Temperature at±5 V (300 Amplifiers)
3.0
2.5
2.0
1.5
1.0
SUPPLY CURRENT – mA
0.5
0
013123456789101112
SUPPLY VOLTAGE – ⴞV
TPC 7. Supply Current vs. Supply Voltage
TPC 5. Input Offset Voltage Drift
3.05
2.95
2.85
2.75
SUPPLY CURRENT – mA
2.65
2.55 40
25 85 125
TEMPERATURE – ⴗC
VS = ⴞ13V
TPC 8. Supply Current vs. Temperature at±13 V
TPC 6. Input Bias Current vs. Common-Mode Voltage
2.65 VS = ⴞ5V
2.60
2.55
2.50
2.45
2.40
SUPPLY CURRENT – mA
2.35
2.30
40
25 85 125
TEMPERATURE – ⴗC
TPC 9. Supply Current vs.
±
Temperature at
5 V
REV. D
–5–
AD8610/AD8620
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
OUTPUT VOLTAGE TO SUPPLY RAIL– V
0
RESISTANCE LOAD –
TPC 10. Output Voltage to Supply Rail vs. Load
12.05 VS = ⴞ13V
= 1k
R
L
12.00
11.95
11.90
11.85
OUTPUT VOLTAGE HIGH – V
11.80
40
25 85 125
TEMPERATURE – ⴗC
TPC 13. Output Voltage High
±
vs. Temperature at
13 V
VS = 13V
4.25 VS = ⴞ5V
= 1k
R
L
4.20
4.15
4.10
4.05
OUTPUT VOLTAGE HIGH – V
4.00
100M10M1M100k10k1k100
3.95
40
25 85 125
TEMPERATURE – ⴗC
TPC 11. Output Voltage High vs.
±
Temperature at
11.80
11.85
11.90
11.95
OUTPUT VOLTAGE LOW – V
12.00
12.05
40
5 V
25 85 125
TEMPERATURE – ⴗC
VS = ⴞ13V
= 1k
R
L
TPC 14. Output Voltage Low vs. Temperature at±13 V
OUTPUT VOLTAGE LOW – V
3.95
4.00
4.05
4.10
4.15
4.20
4.25
4.30
40
25 85 125
TEMPERATURE – ⴗC
VS = ⴞ5V RL = 1k
TPC 12. Output Voltage Low vs.
±
Temperature at
120
VS = ⴞ13V
100
R
= 1k
L
MARKER AT 27MHz
80
= 69.5
M
C
= 20pF
L
60
40
20
0
GAIN – dB
20
40
60
80
1
FREQUENCY – MHz
5 V
10
TPC 15. Open-Loop Gain and Phase vs. Frequency
270
225
180
135
90
45
0
45
90
135
180
200100
PHASE – Degrees
60
40
G = 100
20
G = 10
0
G = 1
CLOSED-LOOP GAIN – dB
20
40
10k 100k 1M1k 10M 100M
FREQUENCY – Hz
V
S
RL = 2k C
L
TPC 16. Closed-Loop Gain vs. Frequency
= ⴞ13V
= 20pF
260
240
220
200
180
– V/mV
VO
A
160
140
120
100
40
25 85 125
TEMPERATURE – ⴗC
= ⴞ13V
V
S
= ⴞ10V
V
O
= 1k
R
L
TPC 17. AVO vs. Temperature at±13 V
190
180
170
160
150
– V/mV
140
VO
A
130
120
110
100
40
25 85 125
TEMPERATURE – ⴗC
VS = ⴞ5V
= ⴞ3V
V
O
RL = 1k
TPC 18. AVO vs. Temperature at±5 V
REV. D–6–
AD8610/AD8620
M
160
140
120
100
80
60
40
PSRR – dB
20
0
–20
–40
+PSRR
–PSRR
FREQUENCY – Hz
= ⴞ13V
V
S
60M10k 100k 1M 10M100 1k
TPC 19. PSRR vs. Frequency at ±13 V
140
120
100
80
60
CMRR – dB
40
20
0
10 60M10k 100k 1M 10M100 1k
FREQUENCY – Hz
V
S
= ⴞ13V
TPC 22. CMRR vs. Frequency
160
140
120
100
80
60
40
PSRR – dB
20
0
–20
–40
–PSRR
10k 100k 1M 10M100 1k FREQUENCY – Hz
+PSRR
V
S
= ⴞ5V
60
TPC 20. PSRR vs. Frequency at ±5 V
VS = ⴞ13V VIN = 300mV p-p
= ⴚ100
A
V
= 10k
R
L
0V
CH2 = 5V/DIV
VOLTA GE – 300mV/DIV
0V
V
IN
V
OUT
TIME – 4␮s/DIV
TPC 23. Positive Overvoltage Recovery
122
121
120
119
PSRR – dB
118
117
116
40
25 85
TEMPERATURE – ⴗC
125
TPC 21. PSRR vs. Temperature
VS = ⴞ13V
= 300mV p-p
V
IN
= ⴚ100
A
V
= 10k
R
L
= 0pF
C
L
V
0V
VOLTA GE – 300mV/DIV
CH2 = 5V/DIV
IN
V
OUT
TIME – 4␮s/DIV
TPC 24. Negative Overvoltage Recovery
0V
V
= ⴞ13V
S
p-p = 1.8␮V
V
IN
P-P VOLTAGE NOISE – 1␮V/DIV
TIME – 1s/DIV
TPC 25. 0.1 Hz to 10 Hz Input Voltage Noise
1,000
VSY = ⴞ13V
100
10
VOLTA G E NOISE DENSITY – nV/ Hz
1
11M100 10k10 1k 100k
FREQUENCY – Hz
TPC 26. Input Voltage Noise vs. Frequency
100
90
80
70
60
50
OUT
Z
40
30
20
10
GAIN = 100
0
1k 100M10k 100k 1M 10M
TPC 27. Z
GAIN = 10
FREQUENCY – Hz
vs. Frequency
OUT
VS = ⴞ13V
GAIN = 1
REV. D
–7–
AD8610/AD8620
100
90
80
70
60
50
OUT
Z
40
30
20
10
0
GAIN = 100
1k 100M10k 100k 1M 10M
TPC 28. Z
40
VS = ⴞ5V
35
= 2k
R
L
= 100mV
V
IN
30
25
20
15
10
SMALL SIGNAL OVERSHOOT – %
5
0
1 10k10 100 1k
CAPACITANCE – pF
GAIN = 10
FREQUENCY – Hz
vs. Frequency
OUT
+OS
VS = ⴞ5V
GAIN = 1
OS
TPC 31. Small Signal Overshoot vs. Load Capacitance
3000
2500
2000
1500
– pA
B
I
1000
500
0
025
TEMPERATURE – ⴗC
85 125
TPC 29. Input Bias Current vs. Temperature
VS = ⴞ13V VIN = ⴞ14V
= +1
A
V
VOLTA GE – 5V/DIV
FREQ = 0.5kHz
V
TIME – 400␮s/DIV
OUT
V
IN
TPC 32. No Phase Reversal
40
VS = ⴞ13V
= 2k
R
35
L
= 100mV p-p
V
IN
30
25
20
15
10
SMALL SIGNAL OVERSHOOT – %
5
0
1 10k10 100 1k
CAPACITANCE – pF
+OS
OS
TPC 30. Small Signal Overshoot vs. Load Capacitance
VOLTA GE – 5V/DIV
VS = ⴞ13V
p-p = 20V
V
IN
= +1
A
V
R
= 2k
L
= 20pF
C
L
TIME – 1␮s/DIV
TPC 33. Large Signal Response at G = +1
VOLTA GE – 5V/DIV
TIME – 400ns/DIV
TPC 34. +SR at G = +1
VS = ⴞ13V
p-p = 20V
V
IN
= +1
A
V
= 2k
R
L
= 20pF
C
L
VOLTA GE – 5V/DIV
VS = ⴞ13V
p-p = 20V
V
IN
= +1
A
V
R
= 2k
L
= 20pF
C
L
TIME – 400ns/DIV
TPC 35. –SR at G = +1
VOLTA GE – 5V/DIV
VS = ⴞ13V V
p-p = 20V
IN
= ⴚ1
A
V
R
= 2k
L
= 20pF
C
L
TIME – 1␮s/DIV
TPC 36. Large Signal Response at G = –1
REV. D–8–
AD8610/AD8620
FREQUENCY – kHz
0 350
50 100
150 200 250
300
138
136
120
128
126
124
122
132
130
134
CS – dB
VS = ⴞ13V
p-p = 20V
V
IN
= ⴚ1
A
V
= 2k
R
L
SR = 50V/␮s C
= 20pF
L
VOLTA GE – 5V/DIV
TIME – 400ns/DIV
TPC 37. +SR at G = –1
CS(dB) = 20 log (V
+
V
IN
20V p-p
0
/ 10 ⴛ VIN)
OUT
+13V
U1
3
V+
2
V–
–13V
Figure 1. Channel Separation Test Circuit

FUNCTIONAL DESCRIPTION

The AD8610/AD8620 is manufactured on Analog Devices, Inc.’s proprietary XFCB (eXtra Fast Complementary Bipolar) process. XFCB is fully dielectrically isolated (DI) and used in conjunc­tion with N-channel JFET technology and trimmable thin-film resistors to create the world’s most precise JFET input amplifier. Dielectrically isolated NPN and PNP transistors fabricated on XFCB have F
greater than 3 GHz. Low TC thin film resistors
T
enable very accurate offset voltage and offset voltage tempco trimming. These process breakthroughs allowed Analog Devices’ world class IC designers to create an amplifier with faster slew rate and more than 50% higher bandwidth at half of the current consumed by its closest competition. The AD8610 is uncondi­tionally stable in all gains, even with capacitive loads well in excess of 1 nF. The AD8610B achieves less than 100 µV of offset and 1 µV/°C of offset drift, numbers usually associated with very high precision bipolar input amplifiers. The AD8610 is offered in the tiny 8-lead MSOP as well as narrow 8-lead SOIC surface­mount packages and is fully specified with supply voltages from ±5 V to ±13 V. The very wide specified temperature range, up to 125°C, guarantees superior operation in systems with little or no active cooling.
The unique input architecture of the AD8610 features extremely low input bias currents and very low input offset voltage. Low power consumption minimizes the die temperature and maintains the very low input bias current. Unlike many competitive JFET amplifiers, the AD8610/AD8620 input bias currents are low even at elevated temperatures. Typical bias currents are less than 200 pA at 85°C. The gate current of a JFET doubles every 10°C resulting in a similar increase in input bias current over temperature. Special care should be given to the PC board layout to minimize leakage currents between PCB traces. Improper layout and board handling generates leakage current that exceeds the bias current of the AD8610/AD8620.
REV. D
R4
2k
0
VS = ⴞ13V V AV = ⴚ1 R SR = 55V/␮s
C
5
2k
0
p-p = 20V
IN
= 2k
L
= 20pF
L
R1
20k
V–
V+
U2
VOLTA GE – 5V/DIV
TIME – 400ns/DIV
TPC 38. –SR at G = –1
R2
6
2k
7
0
0
Figure 2. AD8620 Channel Separation Graph

Power Consumption

A major advantage of the AD8610/AD8620 in new designs is the saving of power. Lower power consumption of the AD8610 makes it much for high-density
more attractive for portable instrumentation and
systems, simplifying thermal management, and
reducing power supply performance requirements. Compare the
consumption
power
of the AD8610/AD8620 versus the OPA627
in Figure 3.
8
7
OPA627
6
5
4
SUPPLY CURRENT – mA
3
AD8610
2
–75 125–50
–25 0 25 50 75 100
TEMPERATURE – ⴗC
Figure 3. Supply Current vs. Temperature
–9–
AD8610/AD8620

Driving Large Capacitive Loads

The AD8610 has excellent capacitive load driving capability and can safely drive up to 10 nF when operating with ±5 V supply. Figures 4 and 5 compare the AD8610/AD8620 against the OPA627 in the noninverting gain configuration driving a 10 kresistor and 10,000 pF capacitor placed in parallel on its output, with a square wave input set to a frequency of 200 kHz. The AD8610 has much less ringing than the OPA627 with heavy capacitive loads.
VS = ⴞ5V R
= 10k
L
= 10,000pF
C
L
VOLTA GE – 20mV/DIV
TIME – 2␮s/DIV
Figure 4. OPA627 Driving CL = 10,000 pF
VS = ⴞ5V
R
= 10k
L
C
= 10,000pF
L
+5V
3
VIN = 50mV
2k 2k
7
2
4
–5V
2F
Figure 6. Capacitive Load Drive Test Circuit
VS = ⴞ5V R
= 10k
L
= 2␮F
C
L
VOLTA GE – 50mV/DIV
TIME – 20␮s/DIV
Figure 7. OPA627 Capacitive Load Drive, AV = +2
VS = ⴞ5V RL = 10k
= 2␮F
C
L
VOLTA GE – 20mV/DIV
TIME – 2␮s/DIV
Figure 5. AD8610/AD8620 Driving CL = 10,000 pF
The AD8610/AD8620 can drive much larger capacitances without any external compensation. Although the AD8610/AD8620 is stable with very large capacitive loads, remember that this capacitive loading will limit the bandwidth of the amplifier. Heavy loads will also increase the amount of overshoot and ringing
capacitive
at the
output. Figures 7 and 8 show the AD8610/AD8620 and the OPA627 in a noninverting gain of +2 driving 2 µF of capacitance load. The

Slew Rate (Unity Gain Inverting vs. Noninverting)

Amplifiers generally have a faster slew rate in an inverting unity gain configuration due to the absence of the differential input capacitance. Figures 9 through 12 show the performance of the AD8610 configured in a gain of –1 compared to the OPA627. The AD8610 slew rate is more symmetrical, and both the positive and negative transitions are much cleaner than in the OPA627.
ringing on the OPA627 is much larger in magnitude and continues more than 10 times longer than the AD8610.
VOLTA GE – 50mV/DIV
TIME – 20␮s/DIV
Figure 8. AD8610/AD8620 Capacitive Load Drive, AV = +2
REV. D–10–
AD8610/AD8620
VS = ⴞ13V
= 2k
R
L
G = –1
SR = 54V/␮s
VOLTA GE – 5V/DIV
TIME – 400ns/DIV
Figure 9. (+SR) of AD8610/AD8620 in Unity Gain of –1
VS = ⴞ13V RL = 2k G = –1
SR = 42.1V/␮s
VOLTA GE – 5V/DIV
TIME – 400ns/DIV
Figure 10. (+SR) of OPA627 in Unity Gain of –1
VS = ⴞ13V
= 2k
R
L
G = –1
SR = 56V/␮s
VOLTA GE – 5V/DIV
TIME – 400ns/DIV
Figure 12. (–SR) of OPA627 in Unity Gain of –1
The AD8610 has a very fast slew rate of 60 V/µs even when config- ured in a noninverting gain of +1. This is the toughest condition to impose on any amplifier since the input common-mode capacitance of the amplifier generally makes its SR appear worse. The slew rate of an amplifier varies according to the voltage difference between its two inputs. To observe the maximum SR as specified in the AD8610 data sheet, a difference voltage of about 2 V between the inputs must be ensured. This will be required for virtually any JFET op amp so that one side of the op amp input circuit is com­pletely off, maximizing the current available to charge and discharge the internal compensation capacitance. Lower differential drive voltages will produce lower slew rate readings. A JFET­input op amp with a slew rate of 60 V/µs at unity gain with
= 10 V might slew at 20 V/µs if it is operated at a gain of
V
IN
+100 with V
= 100 mV.
IN
The slew rate of the AD8610/AD8620 is double that of the OPA627 when configured in a unity gain of +1 (see Figures 13 and 14).
VS = ⴞ13V R
= 2k
L
G = –1
SR = 54V/␮s
VOLTA GE – 5V/DIV
TIME – 400ns/DIV
Figure 11. (–SR) of AD8610/AD8620 in Unity Gain of –1
VS = ⴞ13V R
= 2k
L
G = +1
SR = 85V/␮s
VOLTA GE – 5V/DIV
TIME – 400ns/DIV
Figure 13. (+SR) of AD8610/AD8620 in Unity Gain of +1
REV. D
–11–
AD8610/AD8620
VS = ⴞ13V R
= 2k
L
G = +1
SR = 23V/␮s
VOLTA GE – 5V/DIV
TIME – 400ns/DIV
Figure 14. (+SR) of OPA627 in Unity Gain of +1
The slew rate of an amplifier determines the maximum frequency at which it can respond to a large signal input. This frequency (known as full-power bandwidth, or FPBW) can be calculated from the equation:
FPBW
SR
=
V
×
2π
()
PEAK
for a given distortion (e.g., 1%).
CH1 = 20.8V
p-p
diodes greatly interfere with many application circuits such as precision rectifiers and comparators. The AD8610 is free from these limitations.
+13V
3
7
14V
V1
0
2
–13V
6
4
AD8610
Figure 16. Unity Gain Follower

No Phase Reversal

Many amplifiers misbehave when one or both of the inputs are forced beyond the input common-mode voltage range. Phase reversal is typified by the transfer function of the amplifier, effectively reversing its transfer polarity. In some cases, this can cause lockup and even equipment damage in servo systems, and may cause permanent damage or nonrecoverable parameter shifts to the amplifier itself. Many amplifiers feature compensation circuitry to combat these effects, but some are only effective for the inverting input. The AD8610/AD8620 is designed to prevent phase reversal when one or both inputs are forced beyond their input common-mode voltage range.
V
IN
0V
CH2 = 19.4V
VOLTA GE – 10V/DIV
0V

Input Overvoltage Protection

When the input of an amplifier is driven below VEE or above V by more than one VBE, large currents will flow from the substrate through the negative supply (V–) or the positive supply respectively, to the input pins, which can destroy the device.
p-p
TIME – 400ns/DIV
Figure 15. AD8610 FPBW
(V+),
If the

THD Readings vs. Common-Mode Voltage

Total harmonic distortion of the AD8610/AD8620 is well below
0.0006% with any load down to 600 . The AD8610/AD8620
CC
outperforms the OPA627 for distortion, especially at frequen­cies above 20 kHz.
input source can deliver larger currents than the maximum forward current of the diode (>5 mA), a series resistor can be
added to protect the inputs. With its very low input bias and offset current, a large series resistor can be placed in front of the AD8610 limit current to below damaging levels. Series resistance will generate less than 25 µV of offset. This 10 kΩ will allow
inputs to
of 10 k
input
voltages more than 5 V beyond either power supply. Thermal noise generated by the resistor will add 7.5 nV/Hz to the noise of the AD8610. For the AD8610/AD8620, differential voltages equal to the supply voltage will not cause any problem (see Figure 15). In this context, it should also be noted that the high breakdown voltage of the input FETs eliminates the need to diodes between the inputs of the amplifier, a practice
include clamp
that is
mandatory on many precision op amps. Unfortunately, clamp
VOLTA GE – 5V/DIV
V
OUT
0
TIME – 400␮s/DIV
Figure 17. No Phase Reversal
0.1
0.01
THD+N – %
0.001
0.0001 10 80k
100 1k 10k
FREQUENCY – Hz
VSY = ⴞ13V V
= 5V rms
IN
BW = 80kHz
OPA627
AD8610
Figure 18. AD8610 vs. OPA627 THD + Noise @ VCM = 0 V
REV. D–12–
0.1
ERROR BAND – %
1.2k
1.0k
0
0.001 100.01
SETTLING TIME – ns
0.1 1
800
600
200
400
OPA627
CL – pF
0 2000500
SETTLING TIME –
s
1000 1500
ERROR BAND 0.01%
3.0
2.0
0.0
1.0
2.5
1.5
0.5
VSY = ⴞ13V R
= 600
L
AD8610/AD8620
0.01
THD + N – %
0.001
4V rms
10 20k
2V rms
6V rms
100 1k 10k
FREQUENCY – Hz
Figure 19. THD + Noise vs. Frequency

Noise vs. Common-Mode Voltage

AD8610 noise density varies only 10% over the input range as shown in Table I.
Table I. Noise vs. Common-Mode Voltage
VCM at F = 1 kHz (V) Noise Reading (nV/√Hz)
–10 7.21 –5 6.89
06.73 +5 6.41 +10 7.21

Settling Time

The AD8610 has a very fast settling time, even to a very tight error band, as can be seen from Figure 20. The AD8610 is configured in an inverting gain of +1 with 2 kinput and feedback resistors. The output is monitored with a 10 ×, 10 M, 11.2 pF scope probe.
1.2k
1.0k
800
600
400
SETTLING TIME – ns
200
0
0.001
0.1 1
ERROR BAND – %
100.01
Figure 20. AD8610 Settling Time vs. Error Band
REV. D
–13–
Figure 21. OPA627 Settling Time vs. Error Band
The AD8610/AD8620 maintains this fast settling when loaded with large capacitive loads as shown in Figure 22.
Figure 22. AD8610 Settling Time vs. Load Capacitance
3.0
ERROR BAND 0.01%
2.5
2.0
1.5
1.0
SETTLING TIME – ␮s
0.5
0.0 0 2000500
1000 1500
CL – pF
Figure 23. OPA627 Settling Time vs. Load Capacitance

Output Current Capability

The AD8610 can drive very heavy loads due to its high output current. It is capable of sourcing or sinking 45 mA at ±10 V output. The short circuit current is quite high and the part is capable of sinking about 95 mA and sourcing over 60 mA while operating with
AD8610/AD8620
supplies of ±5 V. Figures 24 and 25 compare the load current versus output voltage of AD8610/AD8620 and OPA627.
10
1
V
EE
V
CC
DELTA FROM RESPECTIVE RAIL – V
0.1
0.00001 1
0.0001 0.001 0.01 0.1 LOAD CURRENT – A
Figure 24. AD8610 Dropout from ±13 V vs. Load Current
10
V
CC
V
1
DELTA FROM RESPECTIVE RAIL – V
0.1
0.00001 1
0.0001 0.001 0.01 0.1
EE
LOAD CURRENT – A
Figure 25. OPA627 Dropout from ±15 V vs. Load Current
Although operating conditions imposed on the AD8610 (±13 V) are less favorable than the OPA627 (±15 V), it can be seen that the AD8610 has much better drive capability (lower headroom to the supply) for a given load current.

Operating with Supplies Greater than ± 13 V

The AD8610 maximum operating voltage is specified at ±13 V. When ±13 V is not readily available, an inexpensive LDO can provide ±12 V from a nominal ±15 V supply.

Input Offset Voltage Adjustment

Offset of AD8610 is very small and normally does not require additional offset adjustment. However, the offset adjust pins can be used as shown in Figure 26 to further reduce the dc offset. By using resistors in the range of 50 kΩ, offset trim range is ±3.3 mV.
+V
S
7
2
3
4
–V
AD8610
5
S
6
1
R1
V
OUT
Figure 26. Offset Voltage Nulling Circuit

Programmable Gain Amplifier (PGA)

The combination of low noise, low input bias current, low input offset voltage, and low temperature drift make the AD8610 a perfect solution for programmable gain amplifiers. PGAs are often used immediately after sensors to increase the dynamic the measurement circuit. Historically, the large ON resistance
range of
of switches, combined with the large IB currents of amplifiers, created a large dc offset in PGAs. Recent and improved monolithic switches
and amplifiers completely remove these problems. A PGA
discrete circuit is shown in Figure 27. In Figure 27, when the 10 pA bias current of the AD8610 is dropped across the (<5 Ω) RON of the switch, it results in a negligible offset error.
When high precision resistors are used, as in the circuit of Figure 27, the error introduced by the PGA is within the 1/2 LSB requirement for a 16-bit system.
+5V
V
IN
G
A
A0
B
A1
74HC139
100
AD8610
U10
5
5pF
1
IN1
Y0
Y1
Y2
Y3
16
IN2
9
IN3
8
IN4
V
LVDD
ADG452
V
SS
4
–5V
–5V
+5V+5V
GND
1312
S1
3
D1
2
S2
14
D2
15
S3
11
D3
10
S4
6
D4
7
5
10k
1k
10k
1k
100
11
V
OUT
G = 1
G = 10
G = 10 0
G = 1000
Figure 27. High Precision PGA
1. Room temperature error calculation due to RON and IB:
∆Ω
VIR
=× = × =
OS B ON
Total Offset Offset V
()
Total Offset Offset Trimmed V
(_ )
Total Offset
VpV V
2510
pA pV
=+
AD8610
=+
AD8610
=+ ≅
510 5
µµ
OS
OS
2. Full temperature error calculation due to RON and IB:
∆ΩVIR
(C)(C) (C)
@@ @85 85 85
°= °× °=
OS B ON
pA . nV
250 15 3 75
×=
3. Temperature coefficient of switch and AD8610/AD8620
combined is essentially the same as the T
∆∆ ∆∆ ∆∆
VTtotal V T V T I R
/( ) /( ) /( )
OS OS OS B ON
∆∆
VTtotal
/( ) . V/C. nV/ C .V/C
OS
=+× =°+ °≅°
05 006 05µµ
AD8610
of the AD8610:
CVOS
REV. D–14–
AD8610/AD8620

High Speed Instrumentation Amplifier (IN AMP)

The three op amp instrumentation amplifiers shown in Figure 28 can provide a range of gains from unity up to 1,000 or higher. The instrumentation amplifier configuration features high common­mode rejection, balanced differential inputs, and stable, accurately defined gain. Low input bias currents and fast settling are achieved with the JFET input AD8610/AD8620. Most instrumentation amplifiers cannot match the high frequency performance of this circuit. The circuit bandwidth is 25 MHz at a gain of 1, and close to 5 MHz at a gain of 10. Settling time for the entire circuit is 550 ns to 0.01% for a 10 V step (gain = 10). Note that the resistors around the input pins need to be small enough in value so that the RC time constant they form in combination with stray circuit capacitance does not reduce circuit bandwidth.
V+
V
IN1
1/2 AD8620
U1
V–
C5
10pF
R1 1k
R4 2k
RG
V
IN2
R7
2k
R8 2k
1/2 AD8620
C4 15pF
U
1
V+
AD8610
U2
V–
R5 2k
15pF
V
OUT
R6 2k
C3
In active filter applications using operational amplifiers, the dc accuracy of the amplifier is critical to optimal filter performance. The amplifier’s offset voltage and bias current contribute to output error. Input offset voltage is passed by the filter, and may be amplified to produce excessive output offset. For low frequency applications requiring large value input resistors, bias and offset currents flowing through these resistors will also generate an offset voltage.
At higher frequencies, an amplifier’s dynamic response must be carefully considered. In this case, slew rate, bandwidth, and open­loop gain play a major role in amplifier selection. The slew rate must be both fast and symmetrical to minimize distortion. The amplifier’s bandwidth, in conjunction with the filter’s gain, will dictate the frequency response of the filter. The use of a high perfor­mance
amplifier such as the AD8610/AD8620 will minimize both
dc and ac errors in all active filter applications.

Second-Order Low-Pass Filter

Figure 29 shows the AD8610 configured as a second-order Butterworth low-pass filter. With the values as shown, the corner frequency of the filter will be 1 MHz. The wide bandwidth of the AD8610/AD8620 allows a corner frequency up to tens of megaHertz. The following equations can be used for component selection:
R1 R2
==
User Selected Typical Values
.
1 414
fR
2
π
()( )()
CUTOFF
.
0 707
fR
2
π
()( )()
CUTOFF
C1
C2
=
=
()
1
1
:k k
10 100
ΩΩ
where C1 and C2 are in farads.
C1
22pF
+13V
R2 1k
C2
10pF
Figure 28. High Speed Instrumentation Amplifier

High Speed Filters

The four most popular configurations are Butterworth, Elliptical, Bessel, and Chebyshev. Each type has a response that is optimized for a given characteristic as shown in Table II.
Table II. Filter Types
Type Sensitivity Overshoot Phase Amplitude (Pass Band)
Butterworth Moderate Good Max Flat Chebyshev Good Moderate Nonlinear Equal Ripple Elliptical Best Poor Equal Ripple Bessel (Thompson) Poor Best Linear
REV. D
–15–
V
IN
R2
10kR110k
11pF
C2
AD8610
U1
–13V
5
Figure 29. Second-Order Low-Pass Filter
V
OUT
AD8610/AD8620

High Speed, Low Noise Differential Driver

The AD8620 is a perfect candidate as a low noise differential driver for many popular ADCs. There are also other applications, such as balanced lines, that require differential drivers. The circuit of Figure 30 is a unique line driver widely used in industrial applica­tions. With ±13 V supplies, the line driver can deliver a differential signal of 23 V p-p into a 1 kload. The high slew rate and wide bandwidth of the AD8620 combine to yield a full power bandwidth of 145 kHz while the low noise front end produces a referred-to­input noise voltage spectral density of 6 nV/Hz. The design is a transformerless, balanced transmission system where output common-mode rejection of noise is of paramount importance. Like the transformer-based design, either output can be shorted to ground for unbalanced line driver applications without changing the circuit gain of 1. This allows the design to be easily set to noninverting, inverting, or differential operation.
U2
3
V+
1k
R4
1k
3
V+
6
AD8610
V–
2
R8
0
1k
R9
1k
R3
2
R1
1k
5
6
U3
1
V–
1/2 OF AD8620
V+
7
1/2 OF AD8620
V–
R2
1k
R10 50
R12
1k
R11 50
R13 1k
VO2 – VO1 = VIN
V
1
O
R5 1k
R6 10k
R7 1k
VO2
0
Figure 30. Differential Driver
REV. D–16–

OUTLINE DIMENSIONS

0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
0.50 (0.0196)
0.25 (0.0099)
45
8 0
1.75 (0.0688)
1.35 (0.0532)
SEATING
PLANE
0.25 (0.0098)
0.10 (0.0040)
85
41
5.00 (0.1968)
4.80 (0.1890)
4.00 (0.1574)
3.80 (0.1497)
1.27 (0.0500) BSC
6.20 (0.2440)
5.80 (0.2284)
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
0.10
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
COMPLIANT TO JEDEC STANDARDS MS-012AA
8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
3.00
BSC
AD8610/AD8620
8-Lead Standard Small Outline Package [SOIC]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
85
3.00 BSC
1
PIN 1
0.65 BSC
0.15
0.00
0.38
0.22
COPLANARITY
0.10
COMPLIANT TO JEDEC STANDARDS MO-187AA
4
SEATING PLANE
4.90 BSC
1.10 MAX
0.23
0.08
8 0
0.80
0.60
0.40
REV. D
–17–
AD8610/AD8620

Revision History

Location Page
2/04—Data Sheet changed from REV. C to REV. D.
Changes to SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Changes to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10/02—Data Sheet changed from REV. B to REV. C.
Updated ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Edits to Figure 15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5/02—Data Sheet changed from REV. A to REV. B.
Addition of part number AD8620 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Universal
Addition of 8-Lead SOIC (R-8 Suffix) Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Changes to GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Additions to SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Change to ELECTRICAL SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Additions to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Replace TPC 29 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Add Channel Separation Test Circuit Figure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Add Channel Separation Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Changes to Figure 26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Addition of High-Speed, Low Noise Differential Driver section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Addition of Figure 30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
–18–
REV. D
–19–
C02730–0–2/04(D)
–20–
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