emitterfølgere

An emitter follower, also known as a common collector amplifier, is a type of bipolar junction transistor (BJT) amplifier configuration. In this configuration, the input signal is applied to the base, and the output is taken from the emitter. The collector is connected directly to the DC power supply, hence the name "common collector."

The primary characteristic of an emitter follower is its high voltage gain, which is approximately unity (close to 1). This means it does not significantly amplify the voltage of the input signal. However, it provides a very high current gain and a low output impedance. This makes it an excellent buffer amplifier, capable of driving loads that would otherwise be difficult for a voltage amplifier to handle due to their low impedance.

The input impedance of an emitter follower is relatively high, which helps to minimize the loading effect on the preceding stage. The output impedance is low, allowing it to efficiently transfer power to a load. This impedance transformation property is its most significant advantage.

Emitter followers are commonly used in applications where impedance matching is crucial, such as in audio output stages, as drivers for power transistors, or in high-frequency circuits where maintaining signal integrity is important. Despite its low voltage gain, its ability to boost current and provide a low output impedance makes it a valuable circuit in electronics design.