CommonEmitterVerstärker

A Common Emitter amplifier is a fundamental building block in analog electronics. It uses a bipolar junction transistor (BJT) or a field-effect transistor (FET) where the input signal is applied to the base (for a BJT) or gate (for a FET), and the output is taken from the collector (for a BJT) or drain (for a FET). The emitter (for a BJT) or source (for a FET) is common to both the input and output circuits, often connected to ground through a resistor or directly.

The primary characteristic of a common emitter amplifier is its high voltage gain and moderate current gain. This configuration also provides a significant phase inversion between the input and output signals, meaning a positive-going input voltage results in a negative-going output voltage, and vice versa. The input impedance is typically moderate, while the output impedance is relatively high.

This amplifier configuration is widely used due to its versatility. It can be employed as a voltage amplifier, an intermediate stage in multi-stage amplifiers, or as part of more complex circuits like oscillators and switching circuits. Its ability to amplify signals makes it crucial in applications ranging from audio amplification to signal processing. Designing a stable and predictable common emitter amplifier involves careful selection of biasing resistors and potentially the use of feedback mechanisms.