<P> Variable pulse width and frequency combines both changes in the pulse width and repetition rate . </P> <P> One classic use for a chopper circuit and where the term is still in use is in chopper amplifiers . These are DC amplifiers . Some types of signals that need amplifying can be so small that an incredibly high gain is required, but very high gain DC amplifiers are much harder to build with low offset and 1 / f (\ displaystyle f) noise, and reasonable stability and bandwidth . It's much easier to build an AC amplifier instead . A chopper circuit is used to break up the input signal so that it can be processed as if it were an AC signal, then integrated back to a DC signal at the output . In this way, extremely small DC signals can be amplified . This approach is often used in electronic instrumentation where stability and accuracy are essential; for example, it is possible using these techniques to construct pico - voltmeters and Hall sensors . </P> <P> The input offset voltage of amplifiers becomes important when trying to amplify small signals with very high gain . Because this technique creates a very low input offset voltage amplifier, and because this input offset voltage does not change much with time and temperature, these techniques are also called "zero - drift" amplifiers (because there is no drift in input offset voltage with time and temperature). Related techniques that also give these zero - drift advantages are auto - zero and chopper - stabilized amplifiers . </P> <P> Auto - zero amplifiers use a secondary auxiliary amplifier to correct the input offset voltage of a main amplifier . Chopper - stabilized amplifiers use a combination of auto - zero and chopper techniques to give some excellent DC precision specifications . </P>

Function of mosfet in the dc chopper circuit