CONNECTION DIAGRAMS
16-Pin SOIC (R-16) Package
Plastic (N-8) and
Cerdip (Q-8) Package
TO-8 (H-12A) Package
LCC (E-20A) Package
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.
a
34 MHz, CBFET
Fast Settling Op Amp
AD843
Analog Devices, Inc., 1995
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
PRODUCT DESCRIPTION
The AD843 is a fast settling, 34 MHz, CBFET input op amp.
The AD843 combines the low (0.6 nA) input bias currents
characteristic of a FET input amplifier while still providing a
34 MHz bandwidth and a 135 ns settling time (to within 0.01%
of final value for a 10 volt step). The AD843 is a member of the
Analog Devices' family of wide bandwidth operational amplifi-
ers. These devices are fabricated using Analog Devices' junction
isolated complementary bipolar (CB) process. This process per-
mits a combination of dc precision and wideband ac perform-
ance previously unobtainable in a monolithic op amp.
The 250 V/
s slew rate and 0.6 nA input bias current of the
AD843 ensure excellent performance in high speed sample-and-
hold applications and in high speed integrators. This amplifier is
also ideally suited for high bandwidth active filters and high fre-
quency signal conditioning circuits.
Unlike many high frequency amplifiers, the AD843 requires no
external compensation and it remains stable over its full operat-
ing temperature range. It is available in five performance grades:
the AD843J and AD843K are rated over the commercial
temperature range of 0
C to +70
C. The AD843A and AD843B
are rated over the industrial temperature range of 40
C to +85
C.
The AD843S is rated over the military temperature range of 55
C
to +125
C and is available processed to MIL-STD-883B, Rev. C.
FEATURES
AC PERFORMANCE
Unity Gain Bandwidth: 34 MHz
Fast Settling: 135 ns to 0.01%
Slew Rate: 250 V/ s
Stable at Gains of 1 or Greater
Full Power Bandwidth: 3.9 MHz
DC PERFORMANCE
Input Offset Voltage: 1 mV max (AD843K/B}
Input Bias Current: 0.6 nA typ
Input Voltage Noise: 19 nV/
Hz
Open Loop Gain: 30 V/mV into a 500 Load
Output Current: 50 mA min
Supply Current: 13 mA max
Available in 8-Pin Plastic Mini-DIP & Cerdip, 16-Pin SOIC,
20-Pin LCC and 12-Pin Hermetic Metal Can Packages
Available in Tape and Reel in Accordance with
EIA-481A Standard
Chips and MIL-STD-883B Parts Also Available
APPLICATIONS
High Speed Sample-and-Hold Amplifiers
High Bandwidth Active Filters
High Speed Integrators
High Frequency Signal Conditioning
The AD843 is offered in either 8-pin plastic DIP or hermetic
cerdip packages, in 16-pin SOIC, 20-Pin LCC, or in a 12-pin
metal can. Chips are also available.
PRODUCT HIGHLIGHTS
1. The high slew rate, fast settling time and low input bias cur-
rent of the AD843 make it the ideal amplifier for 12-bit D/A
and A/D buffers, for high speed sample-and-hold amplifiers
and for high speed integrator circuits. The AD843 can re-
place many FET input hybrid amplifiers such as the
LH0032, LH4104 and OPA600.
2. Fully differential inputs provide outstanding performance in
all standard high frequency op amp applications such as sig-
nal conditioning and active filters.
3. Laser wafer trimming reduces the input offset voltage to
1 mV max (AD843K and AD843B).
4. Although external offset nulling is unnecessary in many ap-
plications, offset null pins are provided.
5. The AD843 does not require external compensation at
closed loop gains of 1 or greater.
AD843J/A
AD843K/B
AD843S
1
Model
Conditions
Min
Typ
Max
Min
Typ
Max
Min
Typ
Max
Units
INPUT OFFSET VOLTAGE
1
1.0
2.0
0.5
1.0
1.0
2.0
mV
T
MIN
-T
MAX
1.7
4.0
1.2
2.0
3.0
4.5
mV
Offset Drift
12
12
35
12
V/
C
INPUT BIAS CURRENT
Initial (T
J
= +25
C)
50
40
50
pA
Warmed-Up
2
0.8
2.5
0.6
1.0
0.8
2.5
nA
T
MIN
-T
MAX
60/160
23/65
2600
nA
INPUT OFFSET CURRENT
Initial (T
J
= +25
C)
30
20
30
pA
Warmed-Up
2
0.25
1.0
0.2
0.4
0.25
1.0
nA
T
MIN
-T
MAX
23/64
9/26
1025
nA
INPUT CHARACTERISTICS
Input Resistance
10
10
10
10
10
10
Input Capacitance
6
6
6
pF
INPUT VOLTAGE RANGE
Common Mode
10
+12,
10
+12,
10
+12,
V
13
13
13
COMMON-MODE REJECTION
V
CM
=
10 V
60
72
70
76
60
72
dB
T
MIN
-T
MAX
60
72
68
76
60
72
dB
INPUT VOLTAGE NOISE
f = 10 kHz
19
19
19
nV/
Hz
Wideband Noise
10 Hz to 10 MHz
60
60
60
V rms
OPEN LOOP GAIN
V
O
=
10 V
R
LOAD
500
15
25
20
30
15
30
V/mV
T
MIN
-T
MAX
10
20
10
25
10
25
V/mV
OUTPUT CHARACTERISTICS
Voltage
R
LOAD
500
10
+11.5,
10
+11.5,
10
+11.5,
V
12.6
12.6
12.6
Current
V
OUT
=
10 V
50
50
50
mA
Output Resistance
Open Loop
12
12
12
FREQUENCY RESPONSE
Unity Gain Bandwidth
V
OUT
= 90 mV p-p
34
34
34
MHz
Full Power Bandwidth
3
V
O
= 20 V p-p
R1
500
2.5
3.9
2.5
3.9
2.5
3.9
MHz
Rise Time
A
VCL
= 1
10
10
10
ns
Overshoot
A
VCL
= 1
15
15
15
%
Slew Rate
A
VCL
= 1
160
250
160
250
160
250
V/
s
Settling Time
10 V Step
A
VCL
= 1
to 0.1%
95
95
95
ns
to 0.01%
135
135
135
ns
Overdrive Recovery
Overdrive
200
200
200
ns
+Overdrive
700
700
700
ns
Differential Gain
f = 4.4 MHz
0.025
0.025
0.025
%
Differential Phase
f = 4.4 MHz
0.025
0.025
0.025
Degree
POWER SUPPLY
Rated Performance
15
15
15
V
Operating Range
4.5
18
4.5
18
4.5
18
V
Quiescent Current
12
13
12
13
12
13
mA
T
MIN
-T
MAX
12.3
14
12.3
14
12.5
16
mA
Rejection Ratio
5 V to
18 V
65
76
70
80
65
76
dB
Rejection Ratio
T
MIN
-T
MAX
62
76
68
80
62
76
dB
TEMPERATURE RANGE
Operating, Rated Performance
Commercial (0
C to +70
C)
AD843J
AD843K
Industrial ( 40
C to +85
C)
AD843A
AD843B
Military (55
C to +125
C)
4
AD843S
PACKAGE OPTIONS
Plastic (N-8)
AD843JN
AD843KN
Cerdip (Q-8)
AD843AQ
AD843BQ
AD843SQ, AD843SQ/883B
Metal Can (H-12A)
AD843BH
AD843SH, AD843SH/883B
LCC (E-20A)
AD843SE/883B
SOIC (R-16)
AD843JR16
Tape & Reel
AD843JR-16REEL
AD843JR-16REEL7
Chips
AD843JCHIPS
AD843SCHIPS
AD843SPECIFICATIONS
REV. D
2
(@ T
A
= +25
C and
15 V dc,
unless otherwise noted)
AD843
REV. D
3
NOTES
1
Standard Military Drawings Available: 5962-9098001M2A (SE/883B), 5962-9098001MXA (SH/883B), 5962-9098001MPA (SQ/883B).
2
Specifications are guaranteed after 5 minutes at T
A
= +25
C.
3
Full power bandwidth = Slew Rate/2
V peak.
4
All "S" grade T
MIN
-T
MAX
specifications are tested with automatic test equipment at T
A
= 55
C and T
A
= +125
C.
Specifications subject to change without notice.
Specifications in boldface are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels. All min and
max specifications are guaranteed although only those shown in boldface are tested on all production units.
ABSOLUTE MAXIMUM RATINGS
1
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18 V
Internal Power Dissipation
2
Plastic Package . . . . . . . . . . . . . . . . . . . . . . . . . . 1.50 Watts
Cerdip Package . . . . . . . . . . . . . . . . . . . . . . . . . 1.35 Watts
12-Pin Header Package . . . . . . . . . . . . . . . . . . . 1.80 Watts
16-Pin SOIC Package . . . . . . . . . . . . . . . . . . . . 1.50 Watts
20-Pin LCC Package . . . . . . . . . . . . . . . . . . . . . . 1.00 Watt
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
V
S
Output Short Circuit Duration . . . . . . . . . . . . . . . . Indefinite
Differential Input Voltage . . . . . . . . . . . . . . . . . . +V
S
and V
S
Storage Temperature Range (N, R) . . . . . . . 65
C to +125
C
Storage Temperature Range (Q, H, E) . . . . 65
C to +150
C
Operating Temperature Range
AD843J/R . . . . . . . . . . . . . . . . . . . . . . . . . . . 0
C to +70
C
AD843A/B . . . . . . . . . . . . . . . . . . . . . . . . . 40
C to +85
C
AD843S . . . . . . . . . . . . . . . . . . . . . . . . . . 55
C to +125
C
Lead Temperature Range (Soldering 60 sec) . . . . . . . . +300
C
ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 V
NOTES
1
Stresses above those listed under "Absolute Maximum Ratings" may cause
permanent damage to 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
8-Pin Plastic Package:
JA
= 100
C/Watt
8-Pin Cerdip Package:
JA
= 110
C/Watt
12-Pin Header Package:
JA
= 80
C/Watt
16-Pin SOIC Package:
JA
= 100
C/Watt
20-Pin LCC Package:
JA
= 150
C/Watt
METALIZATION PHOTOGRAPH
Contact factory for latest dimensions.
Dimensions shown in inches and (mm).
Figure 1. Input Voltage Range vs.
Supply Voltage
REV. D
4
AD843Typical Characteristics
Figure 2. Output Voltage Swing vs.
Supply Voltage
Figure 3. Output Voltage Swing vs.
Load Resistance
Figure 4. Quiescent Current vs.
Supply Voltage
Figure 5. Input Bias Current vs.
Junction Temperature
Figure 6. Output Impedance vs.
Frequency
Figure 7. Input Bias Current vs.
Common Mode Voltage
Figure 8. Short Circuit Current
Limit vs. Junction Temperature (T
J
)
Figure 9. Gain Bandwidth Product
vs. Temperature
AD843
REV. D
5
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
vs. Frequency
Figure 17. Input Noise Voltage
Spectral Density
Figure 18. Slew Rate vs.
Temperature
Figure 10. Open Loop Gain and Phase
Margin vs. Frequency
AD843Typical Characteristics
Figure 20a. Inverting Amplifier
Connection
Figure 20b. Inverter Large Signal
Pulse Response. C
F
= 0, C
L
= 10 pF
Figure 21a. Unity Gain Inverter
Circuit for Driving Capacitive
Loads
Figure 21b. Inserter Cap Load
Large Signal Pulse Response.
C
F
= 15 pF, C
L
= 410 pF
Figure 21c. Inverter Cap Load
Small Signal Pulse Response.
C
F
= 15 pF, C
L
= 410 pF
Figure 19. Open Loop Gain vs.
Resistive Load
Figure 20c. Inverter Small Signal
Pulse Response. C
F
= 0, C
L
= 10 pF
Figure 20d. Inverter Large Signal
Pulse Response. C
F
= 5 pF, C
L
= 110 pF
Figure 20e. Inverter Small Signal
Pulse Response. C
F
= 5 pF, C
L
= 110 pF
6
REV. D
AD843
REV. D
7
Figure 22c. Buffer Small
Signal Pulse Response.
C
L
= 10 pF
Figure 22b. Buffer Large
Signal Pulse Response.
C
L
= 10 pF
Figure 22a. Unity Gain Buffer
Amplifier
Figure 23c. Buffer Cap Load Small
Signal Pulse Response. C
F
= 33 pF,
C
L
= 10 pF
Figure 23e. Buffer Cap Load
Small Signal Pulse Response.
C
F
= 33 pF, C
L
= 110 pF
Figure 23d. Buffer Cap Load
Large Signal Pulse Response.
C
F
= 33 pF, C
L
= 110 pF
Figure 23b. Buffer Cap Load
Large Signal Pulse Response.
C
F
= 33 pF, C
L
= 10 pF
Figure 23a. Unity Gain Buffer Circuit
for Driving Capacitive Loads
REV. D
8
AD843
GROUNDING AND BYPASSING
In designing practical circuits using the AD843, the user must
keep in mind that some special precautions are needed when
dealing with high frequency signals. Circuits must be wired us-
ing short interconnect leads. Ground planes should be used
whenever possible to provide both a low resistance, low induc-
tance circuit path and to minimize the effects of high frequency
coupling. IC sockets should be avoided, since their increased
interlead capacitance can degrade the bandwidth of the device.
Power supply leads should be bypassed to ground as close as
possible to the pins of the amplifier. Again, the component leads
should be kept very short. As shown in Figure 24, a parallel
combination of a 2.2
F tantalum and a 0.1
F ceramic disc ca-
pacitor is recommended.
Figure 24. Recommended Power Supply Bypassing for
the AD843 (DIP Pinout)
USING A HEAT SINK
The AD843 consumes less quiescent power than most precision
high speed amplifiers and is specified to operate without using a
heat sink. However, when driving low impedance loads, the cur-
rent applied to the load can be 4 to 5 times greater than the qui-
escent current. This will produce a noticeable temperature rise,
which will increase input bias currents. The use of a small heat
sink, such as the Mouser Electronics #33HS008 is recommended.
Offset Null Configuration (DIP Pinout)
GROUNDING AND BYPASSING
Like most high bandwidth amplifiers, the AD843 is sensitive to
capacitive loading. Although it will drive capacitive loads up to
20 pF without degradation of its rated performance, both an
increased capacitive load drive capability and a "cleaner"
(nonringing) pulse response can be obtained from the AD843
by using the circuits illustrated in Figures 20 to 23. The addi-
tion of a 5 pF feedback capacitor to the unity gain inverter con-
nection (Figure 20a) substantially reduces the circuit's
overshoot, even when it is driving a 110 pF load. This can be
seen by comparing the waveforms of Figures 20b through 20e.
To drive capacitive loads greater than 100 pF, the load should
be decoupled from the amplifier's output by a 10
resistor and
the feedback capacitor, C
F
, should be connected directly be-
tween the amplifier's output and its inverting input (Figure
21a). When using a 15 pF feedback capacitor, this circuit can
drive 400 pF with less than 20% overshoot, as illustrated in Fig-
ures 21b and 21c. Increasing capacitor C
F
to 47 pF also in-
creases the capacitance drive capability to 1000 pF, at the
expense of a 10:1 reduction in bandwidth compared with the
simple unity gain inverter circuit of Figure 20a.
Unity gain voltage followers (buffers) are more sensitive to
capacitive loads than are inverting amplifiers because there is no
attenuation of the feedback signal. The AD843 can drive 10 pF
to 20 pF when connected in the basic unity gain buffer circuit
of Figure 22a.
The 1 k
resistor in series with the AD843's noninverting input
serves two functions: first, together with the amplifier's input
capacitance, it forms a low-pass filter which slows down the
actual signal seen by the AD843. This helps reduce ringing on
the amplifier's output voltage. The resistor's second function is
to limit the current into the amplifier when the differential input
voltage exceeds the total supply voltage.
The AD843 will deliver a much "cleaner" pulse response when
connected in the somewhat more elaborate follower circuit of
Figure 23a. Note the reduced overshoot in Figure 23b and 23c
as compared to Figures 22b and 22c.
For maximum bandwidth, in most applications, input and feed-
back resistors used with the AD843 should have resistance val-
ues equal to or less than 1.5 k
. Even with these low resistance
values, the resultant RC time constant formed between them
and stray circuit capacitances is large enough to cause peaking
in the amplifier's response. Adding a small capacitor, C
F
, as
shown in Figures 20a to 23a will reduce this peaking and flatten
the overall frequency response. C
F
will normally be less than
10 pF in value.
The AD843 can drive resistive loads over the range of 500
to
with no change in dynamic response. While a 499
load was
used in the circuits of Figures 20-23, the performance of these
circuits will be essentially the same even if this load is removed
or changed to some other value, such as 2 k
.
To obtain the "cleanest" possible transient response when driv-
ing heavy capacitive loads, be sure to connect bypass capacitors
directly between the power supply pins of the AD843 and
ground as outlined in "grounding and bypassing."
AD843
REV. D
9
SAMPLE-AND-HOLD AMPLIFIER CIRCUITS
A Fast Switching Sample & Hold Circuit
A sample-and-hold circuit possessing short acquisition time and
low aperture delay can be built using an AD843 and discrete
JFET switches. The circuit of Figure 25 employs five n-channel
JFETs (with turn-on times of 35 ns) and an AD843 op amp
(which can settle to 0.01% in 135 ns). The circuit has an aper-
ture delay time of 50 ns and an acquisition time of 1
s or less.
This circuit is based on a noninverting open loop architecture,
using a differential hold capacitor to reduce the effects of pedes-
tal error. The charge that is removed from CH1 by Q2 and Q3
is offset by the charge removed from CH2 by Q4 and Q5. This
circuit can tolerate low hold capacitor values (approximately
100 pF), which improve acquisition time, due to the small gate-
to-drain capacitance of the discrete JFETs. Although pedestal
error will vary with input signal level, making trimming more
difficult, the circuit has the advantages of high bandwidth and
short acquisition times. In addition, it will exhibit some
nonlinearity because both amplifiers are operating with a com-
mon-mode input. Amplifier A2, however, contributes less than
0.025% linearity error, due to its 72 dB common-mode rejec-
tion ratio.
To make sure the circuit accommodates a wide
10 V input
range, the gates of the JFETs must be connected to a potential
near the 15 V supply. The level-shift circuitry (diode D3, PNP
transistor Q7, and NPN transistor Q6) shifts the TTL level S/H
command to provide for an adequate pinch-off voltage for the
JFET switches over the full input voltage range.
The JFETs Q2, Q3, Q4 and Q5 across the two hold capacitors
ensure signal acquisition for all conditions of V
IN
and V
OUT
when the circuit switches from the sample to the hold mode.
Transistor Q1 provides an extra stage of isolation between the
output of amplifier A1 and the hold capacitor CH1.
When selecting capacitors for use in a sample-and-hold circuit,
the designer should choose those types with low dielectric
absorption and low temperature coefficients. Silvered-mica
capacitors exhibit low (0 to 100 ppm/
C) temperature coeffi-
cients and will still work in temperatures exceeding 200
C. It is
also recommend that the user test the chosen capacitor to insure
that its value closely matches that printed on it since not all
capacitors are fully tested by their manufacturers for absolute
tolerance.
A high speed CB amplifier, A1, follows the input signal. U1, a
dual wideband "T" switch, connects the input buffer amp to
one of the two output amplifiers while selecting the complemen-
tary amplifier to drive the A/D input. For example, when
"select" is at logic high, A1 drives CH1, A2 tracks the input sig-
nal and the output of A3 is connected to the input of the A/D
converter. At the same time, A3 holds an analog value and its
output is connected to the input of the A/D converter. When the
select command goes to logic LOW, the two output amplifiers
alternate functions.
Since the input to the A/D converter is the alternated "held"
outputs from A1 and A2, the offset voltage mismatch of the two
amplifiers will show up as nonlinearity and, therefore, distortion
in the output signal. To minimize this, potentiometers can be
used to adjust the offsets of the output amplifiers until they are
A PING-PONG S/H AMPLIFIER
For improved throughput over the circuit of Figure 25, a "ping-
pong" architecture may be used. A ping-pong circuit overcomes
some of the problems associated with high speed S/H amplifiers
by allowing the use of a larger hold capacitor for a given sample
rate: this will reduce the associated feedthrough, droop and ped-
estal errors.
Figure 26 illustrates a simple, four-chip ping-pong sample-and-
hold amplifier circuit. This design increases throughput by using
one channel to acquire a new sample while another channel
holds the previous sample. Instead of having to reacquire the
signal when switching from hold to sample mode, it alternately
connects the outputs from Channel 1 or from Channel 2 to the
A/D converter. In this case, the throughput is the slew rate and
settling time of the output amplifiers, A2 and A3.
Figure 25. A Fast Switching Sample-and-Hold Amplifier
REV. D
10
AD843
equal. Alternatively, an autocalibration circuit using two D/A
converters can be employed. This can also be used to calibrate
out the effects of offset voltage drift over temperature.
The switch choice, for U1s, is critical in this type of design. The
DG542 utilizes "T" switching techniques on each channel for
exceptionally low crosstalk and for high isolation. The part fur-
ther improves these specifications by using ground pins between
the signal pins. With an input frequency of 5 MHz, crosstalk
and isolation are 85 dB and 75 dB, respectively. A limitation
of this switch is that it operates from a maximum 5 V negative
supply, making bipolar operation more difficult. It is recom-
mended that amplifiers A1, A2 and A3 operate from the same
5 V supply to minimize any potential latch-up problems.
Figure 26. A Ping-Pong Sample-and-Hold Amplifier
Figure 27. Settling Time Test Circuit
AD843
REV. D
11
MEASURING AD843 SETTLING TIME
Figure 28 shows the dynamic response of the AD843 while op-
erating in the settling time test circuit of Figure 27. The input of
the settling time fixture is driven by a flat-top pulse generator.
The error signal output from A1, the AD843 under test, is am-
plified by op amp A2 and then clamped by two high speed
Schottky diodes.
Figure 28. Settling Characteristics: +10 V to 0 V Step.
Upper Trace: Amplified Error Voltage (0.01%/Div)
Lower Trace: Output of AD843 Under Test (5 V/Div)
The error signal is clamped to prevent it from greatly overload-
ing the oscilloscope preamp. A Tektronix oscilloscope preamp
type 7A26 was chosen because it will recover from the approxi-
mately 0.4 volt overload, quickly enough to allow accurate mea-
surement of the AD843's 135 ns settling time. Amplifier A2 is a
very high speed op amp; it provides a voltage gain of 10, provid-
ing a total gain of 5 from the error signal to the oscilloscope input.
A FAST PEAK DETECTOR CIRCUIT
The peak detector circuit of Figure 29, can accurately capture
the amplitude of input pulses as narrow as 200 ns and can hold
their value with a droop rate of less than 20
V/
s. This circuit
will capture the peak value of positive polarity waveforms; to
detect negative peaks, simply reverse the polarity of the two
diodes.
The high bandwidth and 200 V/
s slew rate of amplifier A2, an
AD843, allows the detector's output to "keep up" with its input
thus minimizing overshoot. The low (<1 nA) input current of
the AD843 ensures that the droop rate is limited only by the
reverse leakage of diode D2, which is typically <10 nA for the
type shown. The low droop rate is apparent in Figure 30. The
detector's output (top trace) loses slightly over a volt of the
8 volt peak input value (bottom trace) in 75 ms, or a rate of
approximately 16
V/
s.
Figure 30. Peak Detector Response to 125 Hz Pulse Train
Figure 31. Peak Capture Time
Amplifier A1, an AD847, can drive 680 pF hold capacitor, C
P
,
fast enough to "catch-up" with the next peak in 100 ns and still
settle to the new value in 250 ns, as illustrated in Figure 31.
Reducing the value of capacitor C
P
to 100 pF will maximize the
speed of this circuit at the expense of increased overshoot and
droop. Since the AD847 can drive an arbitrarily large value of
capacitance, C
P
can be increased to reduce droop, at the expense
of response time.
Figure 29. A Fast Peak Detector Circuit
REV. D
12
AD843
C1314b26/95
PRINTED IN U.S.A.
Mini-DIP Package
(N-8)
TO-8 Package
(H-12A)
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
Cerdip Package
(Q-8)
16-Pin SOIC Package
(R-16)
16
9
8
1
0.4133 (10.50)
0.3977 (10.00)
0.4193 (10.65)
0.3937 (10.00)
0.2992 (7.60)
0.2914 (7.40)
PIN 1
SEATING
PLANE
0.0118 (0.30)
0.0040 (0.10)
0.0192 (0.49)
0.0138 (0.35)
0.1043 (2.65)
0.0926 (2.35)
0.0500
(1.27)
BSC
0.0125 (0.32)
0.0091 (0.23)
0.0500 (1.27)
0.0157 (0.40)
8
0
0.0291 (0.74)
0.0098 (0.25)
x 45
LCC Package
(E-20A)
0.082
0.018
(2.085
0.455)
0.350
0.008 SQ
(8.89
0.20) SQ
NO. 1 PIN
INDEX
0.025
0.003
(0.635
0.075)
0.040 x 45
(1.02 x 45
)
REF 3 PLCS
0.020 x 45
(0.51 x 45
)
REF
0.050
(1.27)
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