OP285 Analog Devices, OP285 Datasheet - Page 8

• Manufacturer Part Number: OP285
• Description: Dual, 9 MHz Precision Operational Amplifier
• Manufacturer: Analog Devices

Specifications of OP285

• -3db Bandwidth: 9MHz
• Slew Rate: 22V/µs
• Vos: 35µV
• Ib: 100nA
• # Opamps Per Pkg: 2
• Input Noise (nv/rthz): 6nV/rtHz
• Vcc-vee: 9V to 44V
• Isy Per Amplifier: 2.5mA
• Packages: SOIC

OP285
INPUT
TTL
NOTE
DECOUPLE CLOSE
TOGETHER ON GROUND PLAN
WITH SHORT LEAD LENGTHS.
1N4148
15V
(2MV/ DIV)
TTL CTRL
(5V/ DIV)
15V
V
1.8k
10V
OUT
3
2
1.5k
300pF
+
OP285
–
100
90
10
0%
1/2
+15V
–15V
8
4
A1
5V
0.1 F
1
2N2907
220
0.1 F
0.1 F
1,2 V
2MV
16–20V
16–20V
+
–
0.1 F
0.1 F
5V
2N3904
0.01 F
1k
1k
+
–
DUT
T
V+
V–
(–1V)
V
10 F
REF
0.47 F
+
I
OUT
1N4148
138.9
50NS
1k
R
L
+
–
D1
|V
NS
1k
REF
7A13 PLUG-IN
7A13 PLUG-IN
|
–15V
D2
15k
+15V
2N4416
2N2222A
1/2 OP260AJ
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 oscilloscope’s 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.
222
2k
R
R
G
F
SCHOTTKY DIODES D1–D4 ARE
HEWLETT-PACKARD HP5082-2835
IC1 IS 1/2 OP260AJ
IC2 IS PMI OP41EJ
1k
10k
10k
750
D3
V
IN
IC2
1 F
D4
3
2
OP285
+
–
OUTPUT
(TO SCOPE)
+15V
–15V
1/2
4
8
0.1 F
0.1 F
10 F
10 F
+
1
15k
R
L
V
OUT