Yhteislähdekytkennässä

Yhteislähdekytkennässä, often translated as common-source configuration in English, is a fundamental electronic circuit topology for amplifying signals. It is one of the three basic configurations for field-effect transistors (FETs), along with common-drain and common-gate. In a common-source circuit, the input signal is applied to the gate terminal of the FET, while the output signal is taken from the drain terminal. The source terminal is common to both the input and output circuits, hence the name. This common connection is typically achieved by grounding the source terminal either directly or through a bypass capacitor, which effectively shorts AC signals to ground.

The common-source configuration is characterized by high voltage gain and high input impedance. Its output impedance is moderate. This makes it a versatile building block for various amplifier designs, including audio amplifiers and radio frequency circuits. The circuit operates by modulating the conductivity of the channel between the drain and source through the voltage applied to the gate. A small change in gate voltage results in a large change in drain current, leading to signal amplification. It is also known for its inherent phase inversion, meaning the output signal is 180 degrees out of phase with the input signal. This inversion is a crucial aspect to consider when cascading multiple amplifier stages or when designing feedback networks.