Audio Frequency Transformer
Small iron-core transformer used in the audio-frequency range of 20 to 20,000 Hz are called audio-frequency transtormers. The use of these transformers in electronic circults employed for communications, measurements and control is quite common for the purpose of coupling load to the voltage source. Primarily, the functions of audio-frequency transformers are,
(1) for stepping up the voltage in amplifiers to obtain the required voltage gain and
(2) for decreasing or increasing the load impedance as seen by the voltage source to achieve the impedance matching. They are also employed sometimes for providing a path for dc through primary while isolating it from the secondary.
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