TYPICAL PERFORMANCE CURVES
(CONT)
At T
A
= +25°C,
±V
CC
=
±15VDC,
unless otherwise noted.
OPA27 SMALL SIGNAL TRANSIENT RESPONSE
+60
+40
Output Voltage (mV)
Output Voltage (mV)
+20
0
–20
–40
–60
0
0.5
1
Time (µs)
1.5
2
2.5
+60
+40
+20
0
–20
–40
–60
OPA37 SMALL SIGNAL TRANSIENT RESPONSE
A
VCL
= +1
C
L
= 15pF
A
V
= +5
C
L
= 25pF
0
0.2
0.4
0.6
Time (µs)
0.8
1.0
1.2
OPA27 LARGE SIGNAL TRANSIENT RESPONSE
+6
+4
Output Voltage (V)
+2
0
–2
A
VCL
= +1
–4
–6
0
2
4
6
Time (µs)
8
10
12
Output Voltage (V)
+15
+10
+5
0
–5
OPA37 LARGE SIGNAL TRANSIENT RESPONSE
A
V
= +5
–10
–15
0
1
2
3
Time (µs)
4
5
6
APPLICATIONS INFORMATION
OFFSET VOLTAGE ADJUSTMENT
The OPA27/37 offset voltage is laser-trimmed and will re-
quire no further trim for most applications. Offset voltage
drift will not be degraded when the input offset is nulled with
a 10kΩ trim potentiometer. Other potentiometer values from
1kΩ to 1MΩ can be used but V
OS
drift will be degraded by
an additional 0.1 to 0.2µV/°C. Nulling large system offsets
by use of the offset trim adjust will degrade drift performance
by approximately 3.3µV/°C per millivolt of offset. Large
system offsets can be nulled without drift degradation by
input summing.
The conventional offset voltage trim circuit is shown in
Figure 3. For trimming very small offsets, the higher resolu-
tion circuit shown in Figure 4 is recommended.
The OPA27/37 can replace 741-type operational amplifiers
by removing or modifying the trim circuit.
THERMOELECTRIC POTENTIALS
The OPA27/37 is laser-trimmed to microvolt-level input
offset voltage and for very low input offset voltage drift.
Careful layout and circuit design techniques are necessary to
prevent offset and drift errors from external thermoelectric
potentials. Dissimilar metal junctions can generate small
EMFs if care is not taken to eliminate either their sources
(lead-to-PC, wiring, etc.) or their temperature difference. See
Figure 11.
Short, direct mounting of the OPA27/37 with close spacing
of the input pins is highly recommended. Poor layout can
result in circuit drifts and offsets which are an order of
magnitude greater than the operational amplifier alone.
®
OPA27, 37
8
ETC [ ETC ]
