In this practical you will investigate the operation and characteristics of a Voltage Controlled Oscillator.
A voltage controlled oscillator is just as the name suggests: an oscillator whose frequency is controlled by an externally applied voltage.
Voltage controlled oscillators may be low frequency of the RC oscillator or integrator type, or high frequency of the LC oscillator type.
For more information on oscillators and signal sources see the assignments associated with the Signal Sources workboard, 53-110.
The VCO associated with this practical is of the integrator type, where the applied control voltage determines the time taken to integrate up and down between internally set levels and hence the output frequency. The integrating waveform is internally squared up to give a squarewave output. When no control voltage is applied to a VCO it will oscillate at a frequency determined by the design of the oscillator circuit.
This frequency is called the Free Running Frequency of the VCO.
When a control voltage is applied, the frequency of oscillation will be dependant on the magnitude of that control voltage. The relationship between control voltage and frequency is important when dealing with a VCO.
It is generally quoted in hertz/volt and is often referred to as the VCO Sensitivity. The frequency range over which the VCO can be controlled is also of importance.
The VCO investigated in this practical has its Range adjustable by controls on the workboard.