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: ⴞ5 V to ⴞ13 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 kΩ load, 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
ⴚIN
ⴙIN
Vⴚ
NC = NO CONNECT
8
AD8610
45
NC
Vⴙ
OUT
NULL
8-Lead SOIC
(R-8 Suffix)
1
OUTA
ⴚINA
ⴙINA
Vⴚ
8
AD8620
45
Vⴙ
OUTB
ⴚINB
ⴙINB
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.
(@ VS = ⴞ5.0 V, VCM = 0 V, TA = 25ⴗC, unless otherwise noted.)
ParameterSymbolConditionsMinTypMaxUnit
INPUT CHARACTERISTICS
Offset Voltage (AD8610B)V
Offset Voltage (AD8620B)V
Offset Voltage (AD8610A/AD8620A)V
Input Bias CurrentI
Input Offset CurrentI
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°C80200µV
A
< +125°C80300µV
A
< 125°C90350µV
A
< +125°C150850µV
A
–10+2+10pA
< +85°C–250+130+250pA
A
< +125°C–2.5+1.5+2.5nA
A
–10+1+10pA
< +85°C–75+20+75pA
A
< +125°C–150+40+150pA
A
45100µV
45150µV
85250µV
Input Voltage Range–2+3V
Common-Mode Rejection RatioCMRRV
Large Signal Voltage GainA
Offset Voltage Drift (AD8610B)∆V
Offset Voltage Drift (AD8620B)∆V
VO
/∆T–40°C < TA < +125°C0.51µV/°C
OS
/∆T–40°C < TA < +125°C0.51.5µV/°C
OS
= –2.5 V to +1.5 V9095dB
CM
RL = 1 kΩ, VO = –3 V to +3 V100180V/mV
Offset Voltage Drift (AD8610A/AD8620A)∆VOS/∆T–40°C < TA < +125°C0.83.5µV/°C
OUTPUT CHARACTERISTICS
Output Voltage HighV
Output Voltage LowV
Output CurrentI
OH
OL
OUT
RL = 1 kΩ, –40°C < TA < +125°C3.84V
RL = 1 kΩ, –40°C < TA < +125°C–4–3.8V
V
> ±2 V± 30mA
OUT
POWER SUPPLY
Power Supply Rejection RatioPSRRVS = ±5 V to ±13 V100110dB
Supply Current/AmplifierI
SY
VO = 0 V2.53.0mA
–40°C < TA < +125°C3.03.5mA
DYNAMIC PERFORMANCE
Slew RateSRRL = 2 kΩ4050V/µs
Gain Bandwidth ProductGBP25MHz
Settling Timet
S
AV = +1, 4 V Step, to 0.01%350ns
NOISE PERFORMANCE
Voltage Noiseen p-p0.1 Hz to 10 Hz1.8µV p-p
Voltage Noise Densitye
Current Noise Density i
Input CapacitanceC
n
n
IN
f = 1 kHz6nV/√Hz
f = 1 kHz5fA/√Hz
Differential8pF
Common-Mode15pF
Channel SeparationC
S
f = 10 kHz137dB
f = 300 kHz120dB
Specifications subject to change without notice.
REV. D–2–
AD8610/AD8620
ELECTRICAL SPECIFICATIONS
(@ VS = ⴞ13 V, VCM = 0 V, TA = 25ⴗC, unless otherwise noted.)
ParameterSymbolConditionsMinTypMaxUnit
INPUT CHARACTERISTICS
Offset Voltage (AD8610B)V
OS
45100µV
–40°C < TA < +125°C80200µV
Offset Voltage (AD8620B)V
Offset Voltage (AD8610A/AD8620A)V
Input Bias CurrentI
OS
–40°C < T
OS
+25°C < T
–40°C < T
B
–40°C < T
< +125°C80300µV
A
< 125°C90350µV
A
< +125°C150850µV
A
–10+3+10pA
< +85°C–250+130+250pA
A
45150µV
85250µV
–40°C < TA < +125°C–3.5+3.5nA
Input Offset CurrentI
OS
–40°C < T
< +85°C–75+20+75pA
A
–10+1.5+10pA
–40°C < TA < +125°C–150+40+150pA
Input Voltage Range–10.5+10.5V
Common-Mode Rejection RatioCMRRV
Large Signal Voltage GainA
Offset Voltage Drift (AD8610B)∆V
Offset Voltage Drift (AD8620B)∆V
VO
/∆T–40°C < TA < +125°C0.51µV/°C
OS
/∆T–40°C < TA < +125°C0.51.5µV/°C
OS
= –10 V to +10 V90110dB
CM
RL = 1 kΩ, VO = –10 V to +10 V100200V/mV
Offset Voltage Drift (AD8610A/AD8620A)∆VOS/∆T–40°C < TA < +125°C0.83.5µV/°C
OUTPUT CHARACTERISTICS
Output Voltage HighV
Output Voltage LowV
Output CurrentI
Short Circuit CurrentI
OH
OL
OUT
SC
RL = 1 kΩ, –40°C < TA < +125°C+11.75 +11.84V
RL = 1 kΩ, –40°C < TA < +125°C–11.84 –11.75 V
V
> 10 V±45mA
OUT
±65mA
POWER SUPPLY
Power Supply Rejection RatioPSRRVS = ±5 V to ±13 V100110dB
Supply Current/AmplifierI
SY
VO = 0 V3.03.5mA
–40°C < TA < +125°C3.54.0mA
DYNAMIC PERFORMANCE
Slew RateSRRL = 2 kΩ4060V/µs
Gain Bandwidth ProductGBP25MHz
Settling Timet
S
AV = 1, 10 V Step, to 0.01%600ns
NOISE PERFORMANCE
Voltage Noiseen p-p0.1 Hz to 10 Hz1.8µV p-p
Voltage Noise Densitye
Current Noise Densityi
Input CapacitanceC
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
TemperaturePackagePackage
ModelRangeDescriptionOptionBranding
AD8610AR–40°C to +125°C8-Lead SOICRN-8
AD8610AR-REEL–40°C to +125°C8-Lead SOICRN-8
AD8610AR-REEL7–40°C to +125°C8-Lead SOICRN-8
AD8610ARM-REEL–40°C to +125°C 8-Lead MSOPRM-8B0A
AD8610ARM-R2–40°C to +125°C 8-Lead MSOPRM-8B0A
AD8610ARZ*–40°C to +125°C8-Lead SOICRN-8
AD8610ARZ-REEL*–40°C to +125°C8-Lead SOICRN-8
AD8610ARZ-REEL7*–40°C to +125°C 8-Lead SOICRN-8
AD8610BR–40°C to +125°C 8-Lead SOICRN-8
AD8610BR-REEL–40°C to +125°C8-Lead SOICRN-8
AD8610BR-REEL7–40°C to +125°C8-Lead SOICRN-8
AD8610BRZ*–40°C to +125°C8-Lead SOICRN-8
AD8610BRZ-REEL*–40°C to +125°C8-Lead SOICRN-8
AD8610BRZ-REEL7*–40°C to +125°C 8-Lead SOICRN-8
AD8620AR–40°C to +125°C8-Lead SOICRN-8
AD8620AR-REEL–40°C to +125°C8-Lead SOICRN-8
AD8620AR-REEL7–40°C to +125°C8-Lead SOICRN-8
AD8620BR–40°C to +125°C 8-Lead SOICRN-8
AD8620BR-REEL–40°C to +125°C8-Lead SOICRN-8
AD8620BR-REEL7–40°C to +125°C8-Lead SOICRN-8
*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
ⴚ150
ⴚ250
ⴚ50
INPUT OFFSET VOLTAGE – V
VS = ⴞ13V
50150
250
TPC 1. Input Offset Voltage at±13 V
600
400
200
0
–200
–400
INPUT OFFSET VOLTAGE – V
–600
–402585125
TEMPERATURE – ⴗC
V
S
= ⴞ5V
600
VS = ⴞ13V
400
200
0
ⴚ200
ⴚ400
INPUT OFFSET VOLTAGE – V
ⴚ600
ⴚ40
2585125
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 1.01.4 1.82.22.6
VS = ⴞ5V OR ⴞ13V
TCVOS – V/ⴗC
18
16
14
12
10
8
6
4
NUMBER OF AMPLIFIERS
2
0
ⴚ150
ⴚ250
ⴚ50
INPUT OFFSET VOLTAGE – V
VS = ⴞ5V
50150
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
ⴚ10ⴚ5
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
ⴚ40
2585125
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
ⴚ40
2585125
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
ⴚ40
2585125
TEMPERATURE – ⴗC
TPC 13. Output Voltage High
±
vs. Temperature at
13 V
VS = ⴞ13V
4.25
VS = ⴞ5V
= 1k⍀
R
L
4.20
4.15
4.10
4.05
OUTPUT VOLTAGE HIGH – V
4.00
100M10M1M100k10k1k100
3.95
ⴚ40
2585125
TEMPERATURE – ⴗC
TPC 11. Output Voltage High vs.
±
Temperature at
ⴚ11.80
ⴚ11.85
ⴚ11.90
ⴚ11.95
OUTPUT VOLTAGE LOW – V
ⴚ12.00
ⴚ12.05
ⴚ40
5 V
2585125
TEMPERATURE – ⴗC
VS = ⴞ13V
= 1k⍀
R
L
TPC 14. Output Voltage Low vs.
Temperature at±13 V
OUTPUT VOLTAGE LOW – V
ⴚ3.95
ⴚ4.00
ⴚ4.05
ⴚ4.10
ⴚ4.15
ⴚ4.20
ⴚ4.25
ⴚ4.30
ⴚ40
2585125
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
ⴚ20
ⴚ40
ⴚ60
ⴚ80
1
FREQUENCY – MHz
5 V
10
TPC 15. Open-Loop Gain
and Phase vs. Frequency
270
225
180
135
90
45
0
ⴚ45
ⴚ90
ⴚ135
ⴚ180
200100
PHASE – Degrees
60
40
G = 100
20
G = 10
0
G = 1
CLOSED-LOOP GAIN – dB
ⴚ20
ⴚ40
10k100k1M1k10M100M
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
ⴚ40
2585125
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
ⴚ40
2585125
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 1M10M1001k
TPC 19. PSRR vs. Frequency at ±13 V
140
120
100
80
60
CMRR – dB
40
20
0
1060M10k 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 1M10M1001k
FREQUENCY – Hz
+PSRR
V
S
= ⴞ5V
60
TPC 20. PSRR vs. Frequency at ±5 V
VS = ⴞ13V
VIN = ⴚ300mV p-p
= ⴚ100
A
V
= 10k⍀
R
L
0V
CH2 = 5V/DIV
VOLTA GE – 300mV/DIV
0V
V
IN
V
OUT
TIME – 4s/DIV
TPC 23. Positive Overvoltage Recovery
122
121
120
119
PSRR – dB
118
117
116
ⴚ40
2585
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 – 4s/DIV
TPC 24. Negative Overvoltage
Recovery
0V
V
= ⴞ13V
S
p-p = 1.8V
V
IN
P-P VOLTAGE NOISE – 1V/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
11M10010k101k100k
FREQUENCY – Hz
TPC 26. Input Voltage Noise vs.
Frequency
100
90
80
70
60
– ⍀
50
OUT
Z
40
30
20
10
GAIN = 100
0
1k100M10k100k1M10M
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
1k100M10k100k1M10M
TPC 28. Z
40
VS = ⴞ5V
35
= 2k⍀
R
L
= 100mV
V
IN
30
25
20
15
10
SMALL SIGNAL OVERSHOOT – %
5
0
110k101001k
CAPACITANCE – pF
GAIN = 10
FREQUENCY – Hz
vs. Frequency
OUT
+OS
VS = ⴞ5V
GAIN = 1
ⴚOS
TPC 31. Small Signal Overshoot vs.
Load Capacitance
3000
2500
2000
1500
– pA
B
I
1000
500
0
025
TEMPERATURE – ⴗC
85125
TPC 29. Input Bias Current vs.
Temperature
VS = ⴞ13V
VIN = ⴞ14V
= +1
A
V
VOLTA GE – 5V/DIV
FREQ = 0.5kHz
V
TIME – 400s/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
110k101001k
CAPACITANCE – pF
+OS
ⴚOS
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 – 1s/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 – 1s/DIV
TPC 36. Large Signal Response at G = –1
REV. D–8–
AD8610/AD8620
FREQUENCY – kHz
0350
50100
150200250
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
–75125–50
–250255075100
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 kΩ resistor 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 – 2s/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
= 2F
C
L
VOLTA GE – 50mV/DIV
TIME – 20s/DIV
Figure 7. OPA627 Capacitive Load Drive, AV = +2
VS = ⴞ5V
RL = 10k⍀
= 2F
C
L
VOLTA GE – 20mV/DIV
TIME – 2s/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 – 20s/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 Ω. 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 kΩ
input
voltages more than 5 V beyond either power supply. Thermal noise
generated by the resistor will add 7.5 nV/√Hzto 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 – 400s/DIV
Figure 17. No Phase Reversal
0.1
0.01
THD+N – %
0.001
0.0001
1080k
1001k10k
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
0.001100.01
SETTLING TIME – ns
0.11
800
600
200
400
OPA627
CL – pF
02000500
SETTLING TIME –
s
10001500
ERROR BAND ⴞ0.01%
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
1020k
2V rms
6V rms
1001k10k
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)
–107.21
–56.89
06.73
+56.41
+107.21
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 kΩ input 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
0.11
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 ⴞ0.01%
2.5
2.0
1.5
1.0
SETTLING TIME – s
0.5
0.0
02000500
10001500
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
0.000011
0.00010.0010.010.1
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
0.000011
0.00010.0010.010.1
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
=× = × =
OSBON
Total OffsetOffsetV
()
Total OffsetOffset TrimmedV
(_)
Total Offset
VpV V
2510
pApV
=+
AD8610
=+
AD8610
=+ ≅
510 5
µµ
∆
OS
∆
OS
2. Full temperature error calculation due to RON and IB:
∆ΩVIR
(C)(C) (C)
@@ @858585
°=°×°=
OSBON
pA.nV
250153 75
×=
3. Temperature coefficient of switch and AD8610/AD8620
combined is essentially the same as the T
∆∆∆∆∆∆
VTtotalVTVT IR
/( )/()/()
OSOSOSBON
∆∆
VTtotal
/( ) . V/C. nV/ C.V/C
OS
=+×
=°+ °≅°
0500605µµ
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
:kk
10100
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.
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 kΩ load. 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)
ⴛ 45ⴗ
8ⴗ
0ⴗ
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