A Folded Cascode Circuit

This video describes a folded cascode topology, a modification from a classic cascode topology where a device typically cascodes a similar flavor device (nFET to nFET or pFET to pFET) where a device cascodes a different flavor device (pFET device to an nFET). This topology is often used to fix a voltage in a way that maximizes the circuit headroom. Although a simple version of the circuit is not often used, it is the basis for an important op-amp / transconductance ampliier topology, the folded cascode amplifier.