10 Hz to 10 Khz Voltage Controlled Oscillator

Voltage-controlled oscillator (VCO)  is an oscillator that its frequency is controlled using a voltage signal.  The VCO described here provide both triangular and square wave output. The control voltage can be varied between 5 mV to 5 V, to produce oscillation frequency from 10 Hz to 10 KHz. Here is the schematic diagram of the circuit:

[Source: National Semiconductor Application Note]