Voltage follower circuit

摘要

A voltage follower comprising a first field-effect transistor (MN1) whose gate forms the input of the voltage follower. Further provided is a second field-effect transistor (MN2) whose drain connected to the gate forms the output of the voltage follower. The sources of the two field-effect transistors (MN1, MN2) are connected to each other and to the drain of a third field-effect transistor (MN3) serving as current source and to the gate of which a predefined bias voltage is applied. The invention employs in addition a fourth field-effect transistor (MN4) whose source-drain path is circuited between the output of the voltage follower and the drain of the third field-effect transistor (MN3) and whose gate is connected to the gate of the third field-effect transistor (MN3). As compared to prior art voltage followers the voltage follower in accordance with the invention comprises a wider voltage range in which it can be put to use. This can be made use of e.g. in amplitude shift-keyed (ASK) demodulators incorporating the voltage follower in accordance with the invention and which need to be operated with particularly small supply voltages.