AMP02

REV. D

–10–

OVERVOLTAGE PROTECTION

Instrumentation amplifiers invariably sit at the front end of in-

strumentation systems where there is a high probability of expo-

sure 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 used is to place limiting re-

sistors in series with each input, but this adds noise. The

AMP02 includes internal protection circuitry that limits the in-

put current to

±4 mA for a 60 V differential overload (see Figure

28) with power off,

±2.5 mA with power on.

Figure 28. 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 tem-

perature stability. In addition, each power supply should be

properly bypassed.