Self-contained bias common source amplifier circuit

Self-contained bias common source amplifier circuit

 ②Self-supplied bias common source amplifier circuit. The figure shows a typical self-bias common source amplifier circuit. In the figure, cl and C2 are the input and
output coupling capacitors respectively, which serve to communicate AC and block DC; Ucc is the drain DC voltage source, which provides energy for the amplifier circuit: RD is the drain resistor
, which can convert changes in the drain current into voltage curve changes in order to output a signal voltage; Rs is the source resistor, whose function is to generate
a source-to-ground voltage drop to provide the source The bias voltage establishes a static bias and has the function of current negative feedback; cs is the source bypass capacitor
, which provides a path for the source AC signal to prevent the AC signal from generating negative feedback on ‰.
    Because when the drain current of the field effect transistor is large, the drain current decreases as the temperature rises, so the thermal stability is good. Therefore,
only a self-bias circuit is needed at the source to be very stable.
    The figure shows an example of self-biasing. "Self-bias" refers to the bias voltage generated by the current of the field effect transistor itself. Because
when an N-channel junction field effect transistor operates normally, a negative bias voltage needs to be added between the gate and source. This
is contrary to the fact that the emitter of a transistor requires a forward bias voltage. In order to obtain the required negative bias voltage between the gate and source, a self-generated bias resistor Rs is set. When the source
current flows through L, there will be an upper positive and lower negative voltage drop Us at both ends of Lu. Since the gate is connected to ground through Ib, the gate is at zero potential. In this way, the required negative bias voltage UGs can be obtained between the gate
and the source if the generated voltage is generated . This is the principle of the self-bias common bath amplifier circuit .