OPA121 Datasheet, PDF (5/15 Pages) Burr-Brown (TI) – Low Cost Precision Difet OPERATIONAL AMPLIFIER

TYPICAL PERFORMANCE CURVES (CONT)
T_A = +25°C, V_CC = ±15VDC unless otherwise noted.
LARGE SIGNAL TRANSIENT RESPONSE
+15
SMALL SIGNAL TRANSIENT RESPONSE
+80
+40
0
0
-15
0
25
50
Time(µs)
+40
+80
0
1
2
3
Time(µs)
4
5
INPUT CURRENTS vs INPUT VOLTAGE
WITH ±V_CC PINS GROUNDED
+2
+1
IIN
V
0
Maximum Safe Current
–1
–2
–15
–10
Maximum Safe Current
–5
0
+5
Input Voltage (V)
+10
+15
APPLICATIONS INFORMATION
OFFSET VOLTAGE ADJUSTMENT
The OPA121 offset voltage is laser-trimmed and will require
no further trim for most applications. As with most ampli-
fiers, externally trimming the remaining offset can change
drift performance by about 0.3µV/°C for each 100µV of
adjusted offset. Note that the trim (Figure 1) is similar to
operational amplifiers such as 741 and AD547. The OPA121
can replace most BIFET amplifiers by leaving the external
null circuit unconnected.
INPUT PROTECTION
Conventional monolithic FET operational amplifiers require
external current-limiting resistors to protect their inputs
against destructive currents that can flow when input FET
gate-to-substrate isolation diodes are forward-biased. Most
BIFET amplifiers can be destroyed by the loss of –V_CC.
Unlike BIFET amplifiers, the Difet OPA121 requires input
current limiting resistors only if its input voltage is greater
+V_CC
7
2
OPA121
3
5
4
*
–V_CC
6
1
±10mV Typical
Trim Range
*10k Ω to 1MΩ
Trim Potentiometer
(100kΩ Recommended)
FIGURE 1. Offset Voltage Trim.
than 6V more negative than –V_CC. A 10kΩ series resistor
will limit input current to a safe level with up to ±15V input
levels even if both supply voltages are lost.
Static damage can cause subtle changes in amplifier input
characteristics without necessarily destroying the device. In
precision operational amplifiers (both bipolar and FET types),
®
5
OPA121