source follower

source follower

Shown is a source follower (buffer amplifier) ​​circuit using a differential input buffered operational amplifier circuit that can be used in
impedance conversion circuits. A field effect transistor
(VTl)     is used in the circuit to form a source follower, which is similar to the emitter follower of a transistor. The input impedance of the field effect transistor is very high. The source of the field effect transistor is connected to a transistor VT2, and the base of the transistor It is determined by the voltage dividing resistor to form a constant current circuit. In order to make the gain of the circuit as close to 1 as possible. It is necessary to use a transconductance field effect transistor and a larger load resistor . Using this circuit structure, + is connected to the source circuit with VT2, which is equivalent to increasing the load resistor to meet the requirements of the circuit.