Voltage Controlled Oscillator using NE555

A voltage-controlled oscillator using NE555 The circuit is usually known as a voltage-to-frequency converter as a result of the output frequency will be modified by changing the input voltage. As mentioned in previous blog posts, pin 5 terminal is voltage control terminal and its function is to manage the edge and trigger levels. Normally, the con

trol voltage is +2/3VCC because of the inner voltage divider. However, an external voltage will be applied to the current terminal directly or through a pot, as illustrated in figure, and by adjusting the pot, control voltage can be varied. Voltage across the timing capacitor is depicted in figure, that varies between +Vcontrol and ½ Vcontrol. If control voltage is increased, the capacitor takes a extended to charge and discharge; the frequency, therefore, decreases. so the fre ­quency will be modified by changing the control volt ­age. Incidentally, the control voltage is also created offered through a pot, or it should be output of a transistor circuit, op-amp, or another device.

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