AD AD845JR-16-REEL Precision, 16 mhz cbfet op amp Datasheet

a
FEATURES
Replaces Hybrid Amplifiers in Many Applications
AC PERFORMANCE:
Settles to 0.01% in 350 ns
100 V/ms Slew Rate
12.8 MHz min Unity-Gain Bandwidth
1.75 MHz Full-Power Bandwidth at 20 V p-p
DC PERFORMANCE:
0.25 mV max Input Offset Voltage
5 mV/8C max Offset Voltage Drift
0.5 nA Input Bias Current
250 V/mV min Open-Loop Gain
4 mV p-p max Voltage Noise, 0.1 Hz to 10 Hz
94 dB min CMRR
Available in Plastic Mini-DIP, Hermetic Cerdip and
SOIC Packages. Also Available in Tape and Reel in
Accordance with EIA-481A Standard
PRODUCT DESCRIPTION
The AD845 is a fast, precise, N channel JFET input, monolithic
operational amplifier. It is fabricated using Analog Devices’
complementary bipolar (CB) process. Advanced laser-wafer
trimming technology enables the very low input offset voltage
and offset voltage drift performance to be realized. This precision, when coupled with a slew rate of 100 V/µs, a stable
unity-gain bandwidth of 16 MHz, and a settling time of 350 ns
0.01%—while driving a parallel load of 100 pF and 500 Ω—
represents a combination of features unmatched by any FET
input IC amplifier. The AD845 can easily be used to upgrade
many existing designs which use BiFET or FET input hybrid
amplifiers and, in some cases, those which use bipolar input op
amps.
The AD845 is ideal for use in applications such as active filters,
high speed integrators, photo diode preamps, sample-and-hold
amplifiers, log amplifiers, and in buffering A/D and D/A converters. The 250 µV max input offset voltage makes offset nulling unnecessary in many applications. The common-mode
rejection ratio of 110 dB over a ± 10 V input voltage range
represents exceptional performance for a JFET input high
speed op amp. This, together with a minimum open-loop
gain of 250 V/mV ensures that 12-bit performance is achieved,
even in unity-gain buffer circuits.
Precision, 16 MHz
CBFET Op Amp
AD845
CONNECTION DIAGRAMS
Plastic Mini-DIP (N) Package
and Cerdip (Q) Package
16-Pin SOIC
(R-16) Package
The AD845 conforms to the standard op amp pinout except
that offset nulling is to V+. The AD845J and AD845K grade
devices are available specified to operate over the commercial
0°C to +70°C temperature range. AD845A and AD845B
devices are specified for operation over the –40°C to +85°C
industrial temperature range. The AD845S is specified to operate over the full military temperature range of –55°C to
+125°C. Both the industrial and military versions are available
in 8-pin cerdip packages. The commercial version is available in
an 8-pin plastic mini-DIP and 16-pin SOIC; “J” and “S” grade
chips are also available.
PRODUCT HIGHLIGHTS
1. The high slew rate, fast settling time, and dc precision of the
AD845 make it ideal for high speed applications requiring
12-bit accuracy.
2. The performance of circuits using the LF400, HA2520/2/5,
HA2620/2/5, 3550, OPA605, and LH0062 can be upgraded
in most cases.
3. The AD845 is unity-gain stable and internally compensated.
4. The AD845 is specified while driving 100 pF/500 Ω loads.
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
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: 617/329-4700
Fax: 617/326-8703
AD845–SPECIFICATIONS (@ +258C and 615 V dc, unless otherwise noted)
Model
Conditions
Min
AD845J/A
Typ
Max
Min
AD845K/B
Typ
Max
Min
AD845S
Typ
Max
Units
1
INPUT OFFSET VOLTAGE
Initial Offset
0.7
TMIN–TMAX
Offset Drift
INPUT BIAS CURRENT2
Initial
INPUT OFFSET CURRENT
Initial
0.1
1.5
0.25
0.4
5.0
0.25
1.0
2.0
10
mV
mV
µV/°C
VCM = 0 V
TMIN–TMAX
0.75
2
45/75
0.5
1
18/38
0.75
2
500
nA
nA
VCM = 0 V
TMIN–TMAX
25
300
3/6.5
15
100
1.2/2.6
25
300
20
pA
nA
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
INPUT VOLTAGE RANGE
Differential
Common Mode
Common-Mode Rejection
1.5
2.5
20
1011
4.0
VCM = ± 10 V
610
86
1011
4.0
± 20
+10.5/–13
110
610
94
± 20
+10.5/–13
113
610
86
1011
4.0
kΩ
pF
± 20
+10.5/–13
110
V
V
dB
0.1 Hz to 10 Hz
f = 10 Hz
f = 100 Hz
f = 1 kHz
f = 10 kHz
f = 100 kHz
4
80
60
25
18
12
4
80
60
25
18
12
4
80
60
25
18
12
µV p-p
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
INPUT CURRENT NOISE
f = 1 kHz
0.1
0.1
0.1
pA/√Hz
OPEN-LOOP GAIN
VO = ± 10 V
RLOAD ≥ 2 kΩ
RLOAD ≥ 500 Ω
TMIN–TMAX
500
250
V/mV
V/mV
V/mV
INPUT VOLTAGE NOISE
OUTPUT CHARACTERISTICS
Voltage
RLOAD ≥ 500 Ω
Current
Short Circuit
Output Resistance
Open Loop
FREQUENCY RESPONSE
Small Signal
Full Power Bandwidth3
Rise Time
Overshoot
Slew Rate
Settling Time
Unity Gain
VO = ± 10 V
RLOAD = 500 Ω
200
100
70
500
250
250
125
75
612.5
500
250
200
100
50
612.5
50
5
12.8
16
80
1.75
20
20
100
612.5
50
5
V
mA
Ω
13.6
16
MHz
94
1.75
20
20
100
MHz
ns
%
V/µs
50
5
13.6
16
94
1.75
20
20
100
10 V Step
CLOAD = 100 pF
RLOAD = 500 Ω
to 0.01%
to 0.1%
350
250
350
250
DIFFERENTIAL GAIN
f = 4.4 MHz
0.04
0.04
0.04
%
DIFFERENTIAL PHASE
f = 4.4 MHz
0.02
0.02
0.02
Degree
POWER SUPPLY
Rated Performance
Operating Range
Rejection Ratio
Quiescent Current
64.75
VS = ± 5 to ± 15 V 88
TMIN to TMAX
± 15
± 15
618
110
10
500
12
64.75
95
618
113
10
12
350
250
± 15
64.75
88
110
10
500
618
12
ns
ns
V
V
dB
mA
NOTES
1
Input offset voltage specifications are guaranteed after 5 minutes of operation at T A = +25°C.
2
Bias current specifications are guaranteed maximum at either input after 5 minutes of operation at T A = +25°C.
3
FPBW = slew rate/2 π V peak.
4
“S” grade TMIN–TMAX are tested with automatic test equipment at T A = –55°C and TA = +125°C.
All min and max specifications are guaranteed. Specifications shown in boldface are tested on all production units at final electrical test. Results from these tests are
used to calculate outgoing quality levels.
Specifications subject to change without notice.
–2–
REV. D
AD845
ABSOLUTE MAXIMUM RATINGS 1
METALIZATION PHOTOGRAPH
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 18 V
Internal Power Dissipation2
Plastic Mini-DIP . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 Watts
Cerdip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Watts
16-Pin SOIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Watts
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . + VS
Output Short-Circuit Duration . . . . . . . . . . . . . . . . Indefinite
Differential Input Voltage . . . . . . . . . . . . . . . . . . +VS and –VS
Storage Temperature Range
Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .–65°C to +150°C
N, R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .–65°C to +125°C
Lead Temperature Range (Soldering 60 sec) . . . . . . . . +300°C
Dimensions shown in inches and (mm).
Contact factory for latest dimensions.
NOTES
1
Stresses above those listed under “Absolute Maximum Ratings” may cause
permanent damage to the device. This is a stress rating only, and functional
operation of the device at these or any other conditions above those indicated in
the operational sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability .
2
Mini-DIP package: θJA = 100°C/watt; cerdip package: θJA = 110°C/watt. SOIC
package: θJA = 100°C/W.
SUBSTRATE CONNECTED TO +VS
ORDERING GUIDE
REV. D
Model
Temperature
Range
Package
Description
Package
Option*
AD845JN
AD845KN
AD845JR-16
AD845AQ
AD845BQ
AD845SQ
AD845SQ/883B
5962-8964501PA
AD845JCHIPS
AD845SCHIPS
AD845JR-16-REEL
AD845JR-16-REEL7
0°C to +70°C
0°C to +70°C
0°C to +70°C
–40°C to +85°C
–40°C to +85°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
0°C to +70°C
–55°C to +125°C
0°C to +70°C
0°C to +70°C
8-Pin Plastic Mini-DIP
8-Pin Plastic Mini-DIP
16-Pin SOIC
8-Pin Cerdip
8-Pin Cerdip
8-Pin Cerdip
8-Pin Cerdip
8-Pin Cerdip
Die
Die
Tape & Reel
Tape & Reel
N-8
N-8
R-16
Q-8
Q-8
Q-8
Q-8
Q-8
–3–
AD845–Typical Characteristics
*N = Plastic DIP: Q = Cerdip; R = Small Outline
IC (SOIC).
Figure 1. Input Voltage Swing
vs. Supply Voltage
Figure 4. Quiescent Current vs.
Supply Voltage
Figure 7. Input Bias Current vs.
Common-Mode Voltage
Figure 2. Output Voltage Swing
vs. Supply Voltage
Figure 5. Input Bias Current vs.
Temperature
Figure 8. Short-Circuit Current
–4–
Limit vs. Temperature
Figure 3. Output Voltage Swing
vs. Resistive Load
Figure 6. Magnitude of Output
Impedance vs. Frequency
Figure 9. Unity-Gain Bandwidth
REV. D
AD845
vs. Temperature
vs. Frequency
Spectral Density
Figure 10. Open-Loop Gain and
Phase Margin vs. Frequency
Figure 11. Open-Loop Gain vs.
Supply Voltage
Figure 12. Power Supply
Rejection vs. Frequency
Figure 13. Common-Mode
Rejection vs. Frequency
Figure 14. Large Signal Frequency
Response
Figure 15. Output Swing and
Error vs. Settling Time
Figure 16. Harmonic Distortion
REV. D
Figure 17. Input Noise Voltage
–5–
Figure 18. Slew Rate vs. Temperature
AD845
Figure 19. Recommended Power
Supply Bypassing
Figure 20. AD845 Simplified
Schematic
Figure 21. Offset Null Configuration
Figure 22a. Unity-Gain Follower
Figure 22b. Unity-Gain Follower
Large Signal Pulse Response
Figure 22c. Unity-Gain Follower
Small Signal Pulse Response
Figure 23a. Unity-Gain Inverter
Figure 23b. Unity-Gain Inverter
Large Signal Pulse Response
Figure 23c. Unity-Gain Inverter
Small Signal Pulse Response
–6–
REV. D
AD845
MEASURING AD845 SETTLING TIME
and stable, accurately defined gain. Low input bias currents and
fast settling are achieved with the FET input AD845.
The Figure 24 shows the AD845 settling time performance.
This measurement was accomplished by driving the amplifier
in the unity-gain inverting mode with a fast pulse generator.
The input summing junction was measured using false nulling
techniques.
Most monolithic instrumentation amplifiers do not have the
high frequency performance of the circuit in Figure 26. The circuit bandwidth is 10.9 MHz at a gain of 1 and 8.8 MHz at a
gain of 10; settling time for the entire circuit is 900 ns to 0.01%
for a 10 V step (Gain = 10).
Settling time is defined as:
The interval of time from the application of an ideal
step function input until the closed-loop amplifier output
has entered and remains within a specified error band.
The capacitors employed in this circuit greatly improve the
amplifier’s settling time and phase margin.
Components of settling time include:
1. Propagation time through the amplifier
2. Slewing time to approach the final output value
3. Recovery time from overload associated with the slewing
4. Linear settling to within a specified error band.
These individual components can easily be seen in Figure 24.
Settling time is extremely important in high speed applications
where the current output of a DAC must be converted to a
voltage. When driving a 500 Ω load in parallel with a 100 pF
capacitor, the AD845 settles to 0.1% in 250 ns and to 0.01% in
310 ns.
Figure 26. High Performance, High Speed Instrumentation Amplifier
Table I. Performance Summary for the Three Op Amp
Instrumentation Amplifier Circuit
Figure 24. Settling Characteristics 0 V to 10 V Step
Upper Trace: Output of AD845 Under Test (5 V/Div)
Lower Trace: Error Voltage (1 mV/Div)
Gain
RG
1
2
10
100
Open
2k
226 Ω
20 Ω
3 Op-Amp In-Amp
Small Signal
Bandwidth
10.9 MHz
8.8 MHz
2.6 MHz
290 kHz
Settling Time
to 0.01%
500 ns
500 ns
900 ns
7.5 µs
Note: Resistors around the amplifiers’ input pins need to be small enough in
value so that the RC time constant they form, with stray circuit capacitance,
does not reduce circuit bandwidth.
Figure 25. Settling Time Test Circuit
A HIGH SPEED INSTRUMENTATION AMP
Figure 27. The Pulse Response of the Three Op Amp
Instrumentation Amplifier. Gain = 1, Horizontal Scale:
0.5 ms/Div; Vertical Scale: 5 V/Div
The three op amp instrumentation amplifier circuit shown in
Figure 26 can provide a range of gains from unity up to 1000
and higher. The instrumentation amplifier configuration features high common-mode rejection, balanced differential inputs
REV. D
–7–
C1188c–5–8/94
AD845
Figure 28a. Settling Time of the Three Op Amp Instrumentation Amplifier. Horizontal Scale: 200 ns/Div; Vertical
Scale, Positive Pulse Input: 5 V/Div; Output Settling:
1 mV/Div
Figure 28b. Settling Time of the Three Op Amp Instrumentation Amplifier. Horizontal Scale: 200 ns/Div; Vertical
Scale, Negative Pulse Input: 5 V/ Div; Output Settling:
1 mV/Div
DRIVING THE ANALOG INPUT OF AN A/D CONVERTER
AD845 is ideally suited to drive high resolution A/D converters
with 5 µs on longer conversion times since it offers both wide
bandwidth and high open-loop gain.
An op amp driving the analog input of an A/D converter, such
as that shown in Figure 29, must be capable of maintaining a
constant output voltage under dynamically changing load conditions. In successive approximation converters, the input current
is compared to a series of switched trial currents. The comparison point is diode clamped but may deviate several hundred
millivolts resulting in high frequency modulation of A/D input
current. The output impedance of a feedback amplifier is made
artificially low by the loop gain. At high frequencies, where the
loop gain is low, the amplifier output impedance can approach
its open-loop value. Most IC amplifiers exhibit a minimum
open-loop output impedance of 25 Ω due to current limiting resistors. A few hundred microamps reflected from the change in
converter loading can introduce errors in instantaneous input
voltage. If the A/D conversion speed is not excessive and the
bandwidth of the amplifier is sufficient, the amplifier’s output
will return to the nominal value before the converter makes its
comparison. However, many amplifiers have relatively narrow
bandwidth yielding slow recovery from output transients. The
Figure 29. AD845 As ADC Unity Gain Buffer
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
Cerdip (Q) Package
PRINTED IN U.S.A.
Mini-DIP (N) Package
–8–
REV. D