Audio Frequency Oscillator
The block diagram of audio frequency oscillator is shown in the fig. the audio frequency oscillator is designed to provide an output signal over audio frequency range. The laboratory AFO provides frequency range from 10 Hz to 100 Hz approximately.
Pic 1. Block Diagram Of an Audio Frequency Oscillator
The first block is tunable sinewave oscillator. It is the heart of the instrument. These oscillators are of the wien bridge or phase shift type or beat frequency oscillator. This oscillator provides with a frequency range selector. The output of the sinewave oscillator is applied to amplifier. The amplifier amplifies the signal generated by the oscillator. The amplifier also provides buffering between the oscillator and any load connected to the output terminals.
The amplifier output fed to the attenuation through a switch. The switch select the sinewave output direct from the output of the amplifier. For square wave output the amplifier output is connected to square wave shaping network. The output of wave shaping network is now connected to attenuator. The attenuator has an amplitude control to get the required output voltage from audio oscillator.
Separate dial is provided for frequency measurement. Some audio oscillators use digital frequency counter to display the frequency.
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