AMPLIFIER CIRCUIT

PURPOSE:To keep a voltage between an output and the 3rd terminal constant and to reduce the distortion factor, by connecting an input terminal and the output terminal, and an input terminal of an amplifier element having the 3rd terminal and the 3rd terminal itself in terms of Ac. CONSTITUTION:A gate of an MOSFET is grounded via a resistor 2, a source is connected to a positive voltage source via a resistor 5, and a drain is connected to a negative voltage source 7 via a resistor 12. The source has the output terminal 4, and the input terminal 1 is connected to the gate and also to the source via a capacitor 11. An input signal is represented at the output terminal 4 on the same amplitude level and applied to the drain also via the capacitor 11, then a drain-source voltage VDS is kept constant at all times and its output resistance value is a constnt value, then the distortion factor is not deteriorated even if the drain current is increased.