App note: Advantages and limitations of the chopper-stabilized architecture of zero-drift precision op amps

App note from ON Semiconductors on the do’s and don’ts when using zero-drift precision op amps. Link here (PDF)

Zero−drift precision op amps are specialized op amps designed for applications that require high output accuracy due to small differential voltages. Not only do they feature low input offset voltage, but they also have high CMRR, high PSRR, high open loop gain, and low drift over temperature and time. These features make them ideal for applications such as low−side current sensing and sensor interface, particularly with very small differential signals.

Precision op amps are able to achieve “zero−drift” offset voltage, maintaining low input offset voltage over temperature variation and time, through a number of techniques. One of the ways that an amplifier can achieve this is by using a design technique that periodically measures the input offset voltage and corrects the offset at the output. This type of architecture is referred to as chopper−stabilized. Like all engineering solutions, zero−drift op amps also have their limitations. One of the less obvious is a result of the fact that the internal circuit of the chopper−stabilized amplifier contains a clocked system.

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