Folded Cascode Amplifier

A folded cascode circuit is a type of transistor amplifier that offers high gain, large output swing, and good bandwidth. It is a variation of the cascode circuit, which uses two transistors in series to achieve a higher voltage gain and output impedance than a single transistor.

In a folded cascode circuit, the two transistors in the cascode stage are arranged in a "folded" configuration, with the input signal applied to the base of the first transistor and the output signal taken from the collector of the second transistor. This configuration has several advantages over the traditional cascode circuit, including:

• Higher gain: The folded cascode circuit can achieve high gain, higher than the gain of a single transistor or a traditional cascode circuit.

• Larger output swing: The folded cascode circuit can swing its output to within a few volts of the supply rails, which is important for many applications.

• Good bandwidth: The folded cascode circuit has a good bandwidth, which means that it can amplify high-frequency signals without significant distortion.

• Even better stability: The folded cascode circuit is even more stable than a conventional cascode circuit, as there is less current variation on the supply rails.