APPLICATIONS INFORMATION
OPA132 series op amps are unity-gain stable and suitable
for a wide range of general-purpose applications. Power
supply pins should be bypassed with 10nF ceramic capaci-
tors or larger.
OPA132 op amps are free from unexpected output phase-
reversal common with FET op amps. Many FET-input op
amps exhibit phase-reversal of the output when the input
common-mode voltage range is exceeded. This can occur in
voltage-follower circuits, causing serious problems in
control loop applications. OPA132 series op amps are free
from this undesirable behavior. All circuitry is completely
independent in dual and quad versions, assuring normal
behavior when one amplifier in a package is overdriven or
short-circuited.
OPERATING VOLTAGE
OPA132 series op amps operate with power supplies from
±2.5V
to
±18V
with excellent performance. Although
specifications are production tested with
±15V
supplies,
most behavior remains unchanged throughout the full
operating voltage range. Parameters which vary signifi-
cantly with operating voltage are shown in the typical
performance curves.
OFFSET VOLTAGE TRIM
Offset voltage of OPA132 series amplifiers is laser trimmed
and usually requires no user adjustment. The OPA132
(single op amp version) provides offset voltage trim con-
nections on pins 1 and 8. Offset voltage can be adjusted by
connecting a potentiometer as shown in Figure 1. This
adjustment should be used only to null the offset of the op
amp, not to adjust system offset or offset produced by the
signal source. Nulling offset could degrade the offset
voltage drift behavior of the op amp. While it is not
possible to predict the exact change in drift, the effect is
usually small.
10nF
V+
Trim Range: ±4mV typ
100kΩ
7
2
3
10nF
1
8
OPA132
4
6
OPA132 single op amp only.
Use offset adjust pins only to null
offset voltage of op amp—see text.
V–
FIGURE 1. OPA132 Offset Voltage Trim Circuit.
INPUT BIAS CURRENT
The FET-inputs of the OPA132 series provide very low
input bias current and cause negligible errors in most appli-
cations. For applications where low input bias current is
crucial, junction temperature rise should be minimized. The
input bias current of FET-input op amps increases with
temperature as shown in the typical performance curve
“Input Bias Current vs Temperature.”
The OPA132 series may be operated at reduced power
supply voltage to minimize power dissipation and tempera-
ture rise. Using
±3V
supplies reduces power dissipation to
one-fifth that at
±15V.
The dual and quad versions have higher total power dissipa-
tion than the single, leading to higher junction temperature.
Thus, a warmed-up quad will have higher input bias current
than a warmed-up single. Furthermore, an SOIC will gener-
ally have higher junction temperature than a DIP at the same
ambient temperature because of a larger
θ
JA
. Refer to the
specifications table.
Circuit board layout can also help minimize junction tem-
perature rise. Temperature rise can be minimized by solder-
ing the devices to the circuit board rather than using a socket.
Wide copper traces will also help dissipate the heat by acting
as an additional heat sink.
Input stage cascode circuitry assures that the input bias
current remains virtually unchanged throughout the full
input common-mode range of the OPA132 series. See the
typical performance curve “Input Bias Current vs Common-
Mode Voltage.”
OPA132, 2132, 4132
SBOS054A
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