Datasheet

REV. E–10–
AMP02
Overvoltage Protection
Instrumentation amplifiers invariably sit at the front end of
instrumentation systems where there is a high probability of
exposure to overloads. Voltage transients, failure of a transducer,
or removal of the amplifier power supply while the signal source is
connected may destroy or degrade the performance of an unpro-
tected device. A common technique is to place limiting resistors in
series with each input, but this adds noise. The AMP02 includes
internal protection circuitry that limits the input current to ±4 mA
for a 60 V differential overload (see Figure 5) with power off,
±2.5 mA with power on.
DIFFERENTIAL INPUT VOLTAGE
4
–100
LEAKAGE CURRENT – mA
3
1
–1
–3
–4
2
0
–2
–80 –60 –40 –20 0 20 40 60 80 100
POWER ON
POWER OFF
T
A
= 25ⴗC
V
S
= ⴞ15V
Figure 5. AMP02’s Input Protection Circuitry Limits Input
Current During Overvoltage Conditions
Power Supply Considerations
Achieving the rated performance of precision amplifiers in a
practical circuit requires careful attention to external influences.
For example, supply noise and changes in the nominal voltage
directly affect the input offset voltage. A PSR of 80 dB means
that a change of 100 mV on the supply (not an uncommon
value) will produce a 10 µV input offset change. Consequently,
care should be taken in choosing a power unit that has a low
output noise level, good line and load regulation, and good
temperature stability. In addition, each power supply should be
properly bypassed.