Yhteislähdevahvistin

Yhteislähdevahvistin, also known as a common-source amplifier in English, is a fundamental analog electronic circuit configuration. It is one of the three basic amplifier topologies for field-effect transistors (FETs), alongside the common-drain and common-gate configurations. In a common-source amplifier, the input signal is applied to the gate terminal, the output signal is taken from the drain terminal, and the source terminal is common to both the input and output circuits, usually connected to ground or a constant voltage.

The common-source amplifier is characterized by high voltage gain and high input impedance, while its output impedance is typically moderate. This makes it suitable for amplifying signals from high-impedance sources. The circuit typically employs a load resistor or a current source connected to the drain terminal. A biasing network is also required to set the operating point of the FET in its active region, ensuring proper amplification.

The common-source configuration provides a phase inversion between the input and output signals, meaning a positive-going input voltage results in a negative-going output voltage. This characteristic is important when considering cascading amplifier stages or designing feedback networks. Due to its versatility and performance characteristics, the common-source amplifier is widely used in various applications, including audio amplifiers, radio-frequency circuits, and signal processing systems.