impedance transformer

Impedance converters are electronic circuits that convert a low impedance to a high impedance or a high impedance to a low impedance. Each passive component and active electronic circuit is characterized by its input and/or output imp edance.

Impedance converters are used wherever different impedances need to be matched. For example, in data or high- frequency cables, microphones or loudspeakers, antennas, filters, oscillating circuits or amplifiers. Every component and electronic circuit has an input and/or output impedance that is either high or low impedance. The impedance converter matches this high or low impedance to the impedance of the connected component.

Technically, an impedance converter is an electronic circuit whose input impedance and output impedance are matched to the corresponding components. For example, in a simple transistor circuit with emitter coupling, the signal output at the emitter is lower impedance than at the collector. This matching ensures the maximum possible efficiency in signal transmission. Another impedance matching can be done with a differential amplifier whose negative input is directly connected to the output via a resistor. Thus, the voltage at the negative input of the differential amplifier is identical to the output voltage.

The example of a loudspeaker connected to a power amplifier shows how efficient such matching can be. For example, with a speaker impedance of 8 ohms, the output speaker power is halved compared to the nominal impedance of 4 ohms. Another example is the impedance conversion of a high-impedance condenser microphone to a longer low-impedance microphone cable.