Audio Frequency Transformer

Audio Frequency Transformer: Construction

• Figure (a) shows center taped secondary winding to provide two anti-phase signals. 
• The dot near the winding indicates relative polarity of the signal on different windings. 
• The dot at point P shows secondary winding signal is in phase with primary winding signal whereas the dot at point Q indicates secondary winding signal is antiphase with primary winding signal. 
• Figure (b) shows two audio amplifier is used to couple the power output stage of an audio amplifier to the loud speaker.

Function of Audio Frequency Transformer

• They allow only AC audio signal to the loud speaker whereas preventing DC from the amplifier.
• They provide isolated external connection for the loud speakers.
• They provide impedance matching between low input impedance of loud speaker to higher output impedance of an amplifier. It will allow maximum power transfer from the amplifier to speaker. 

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Application of Audio Frequency Transformer

• The audio frequency transformer works in the frequency range of 20 Hz to 20 kHz. They are used in the audio amplifiers. 
• They are essential in the impedance matching. i.e., matching high impedance output of amplifier to the low impedance of loud speaker.