Chapter: Electronic Circuits : JFET and MOSFET Amplifiers

Small signal Analysis of MOSFET

Common-Source Configuration, Common-Gate Configuration, Source Follower (Common-Drain Configuration)

Small signal Analysis of MOSFET

Common-Source Configuration

This configuration serves as the gain stage. The disadvantage is high output impedance. Capacitor CS is included such that the stage is connected to a current source for biasing

Common-Gate Configuration

This amplifier provides gain and is useful when a specific (low) Rin is required. This is, e.g., the case when the impedance needs to be matched, as with transmission lines (e.g. to 50 Ω). Another application of the CG configuration is that it acts as a current buffer (current gain close to unity, small Rin, large Rout).

Source Follower (Common-Drain Configuration)

This configuration acts as a voltage buffer. It provides no gain, but has low output impedance. It is typically the last stage in a multi-stage amplifier.

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Electronic Circuits : JFET and MOSFET Amplifiers : Small signal Analysis of MOSFET |