A chopper-stabilized amplifier (or other device) has a set of switches that allows the input pin to be disconnected from the input signal and connected to ground (or a zero voltage point). An offset network inside the op amp is then adjusted until the output signal goes to zero, i.e., the input offset voltage is reset to zero. The input pin is then re-connected to the input signal. This switching or 'chopping' action can occur at a frequency of tens of kilohertz up into the hundreds of kilohertz. Since this is a continuous action, the amplifier offset voltage is always nearly at zero, despite changes in temperature or other effects. As an extension of this, 1/f noise can be viewed as a form of changes in the offset, so fairly high-frequency chopping can greatly reduce this also.
