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OP285_15 Datasheet, PDF (8/16 Pages) Analog Devices – Dual 9 MHz Precision Operational Amplifier | |||
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OP285
+15V
0.1â®F
3+ 8
1/2
1
OP285
2â
4
0.1â®F
*
â15V
+ 7A13 PLUG-IN
â 7A13 PLUG-IN
TTL
INPUT
300pF
15V
1.5kâ
1kâ
2N3904
â¬IOUT
|VREF|
1kâ
1N4148
1.8kâ
15V
2N2907
1kâ
220â
10â®F
+
0.1â®F
*NOTE
DECOUPLE CLOSE
TOGETHER ON GROUND PLAN
WITH SHORT LEAD LENGTHS.
0.01â®F
0.47â®F
VREF
(â1V)
Figure 5. Transient Output Load Current Test Fixture
A1
100
TTL CTRL 90
(5V/ DIV)
1,2 V
10V
VOUT 10
(2MV/ DIV) 0%
5V
2MV
T
138.9NS
50NS
Measuring Settling Time
The design of OP285 combines high slew rate and wide gain-
bandwidth product to produce a fast-settling (ts < l µs) amplifier
for 8- and 12-bit applications. The test circuit designed to measure
the settling time of the OP285 is shown in Figure 7. This test
method has advantages over false-sum node techniques in that
the actual output of the amplifier is measured, instead of an
error voltage at the sum node. Common-mode settling effects
are exercised in this circuit in addition to the slew rate and
bandwidth effects measured by the false-sum-node method. Of
course, a reasonably flat-top pulse is required as the stimulus.
The output waveform of the OP285 under test is clamped by
Schottky diodes and buffered by the JFET source follower.
The signal is amplified by a factor of ten by the OP260 and
then Schottky-clamped at the output to prevent overloading
the oscilloscopeâs input amplifier. The OP41 is configured as
a fast integrator which provides overall dc offset nulling.
High Speed Operation
As with most high speed amplifiers, care should be taken with
supply decoupling, lead dress, and component placement. Rec-
ommended circuit configurations for inverting and noninverting
applications are shown in Figures 8 and Figure 9.
+15V
10â®F
+
0.1â®F
2â 8
1/2
1
VOUT
VIN
3
OP285
+
4
RL
15kâ
0.1â®F
Figure 6. OP285âs Output Load Current Recovery Time
10â®F
16â20V
â+
0.1â®F
V+
DUT
Vâ
0.1â®F
+â
16â20V
Ø5V
RL
1kâ
D1
â15V
Figure 8. Unity Gain Follower
+15V
1kâ
D3
2N4416 1/2 OP260AJ
D2
RF
2kâ
RG
222â
10kâ
10kâ
OUTPUT
(TO SCOPE)
D4
1â®F
IC2
1N4148
2N2222A
15kâ
â15V
750â
SCHOTTKY DIODES D1âD4 ARE
HEWLETT-PACKARD HP5082-2835
IC1 IS 1/2 OP260AJ
IC2 IS PMI OP41EJ
Figure 7. OP285âs Settling Time Test Fixture
â8â
REV. A
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