Application of field effect transistors in pocket radio circuits

Application of field effect transistors in pocket radio circuits

(1) Application of field effect transistor fixed bias circuit in double-tube pocket radio circuit
    The picture shown is an ultra-small radio circuit that uses two transistors. This circuit has high sensitivity. In this circuit,
the battery acts as a DC power supply to provide a bias voltage to the drain of the FET through the load resistor R1, making it work in an amplified state.
Various signals in the sky are received by an external antenna , and the AC signals pass through cl and enter the LC resonant circuit . The LC resonant circuit is composed of a magnetic bar coil and a capacitor
. After frequency selection of the resonant circuit , it is coupled to the grid of the Yang effect transistor VR via C4, superimposed with the negative bias of the grid edge, and added to the grid of the FET to make
the field effect The drain current ID of the tube changes accordingly, and a voltage drop occurs on the load resistor RI. After being isolated from DC by c5, it is output, and
the amplified signal voltage is obtained at the output end. The amplified signal is sent to the base of the transistor, which amplifies and outputs a purer audio signal
to the headphones.