Folded Cascode Op-amp :

In order to overcome the drawbacks of telescopic cascode op-amp namely limited output swing, and difficulty in shorting the input and output a “folded cascode” op-amp can be used.

The idea of folding is that in a cascode differential amplifier the input device is replaced by the opposite type while still converting the input voltage to a current as shown in
Figure below.

Fig1-Folded-Cascode-Op-amp.png

An important property of folded cascode op-amps is the capability of handling input common mode levels close to one of the supply rails.

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