Astable Multivibrator (Oscillator)

Posted on Feb 7, 2014

This circuit is an astable multivibrator, or oscillator. The two transistors are cross-coupled in such a way that the circuit switches back and forth between two states. In one state, the base of Q1 is about one diode drop above ground, allowing a base current to flow. This keeps Q1 switched on, in saturation mode, allowing a current to flow throu

Astable Multivibrator (Oscillator)
Click here to download the full size of the above Circuit.

gh the collector, keeping Q1`s collector voltage low, and discharging C1. Q2 is switched off, because its base voltage is not high enough to switch it on. As the collector current into Q1 charges C1, the base voltage for Q2 goes up, until it is high enough to switch on Q2, causing a current to flow through its collector, which drops the collector voltage (the current causes a voltage drop across the resistor above it). The right side of C2 has dropped, but the voltage across it hasn`t changed, so this causes Q1`s base voltage to drop below ground, switching it off.

Leave Comment

characters left:

New Circuits



Popular Circuits

Touch Light Dimmer circuit
Audio Oscillator with Frequency Counter
avr Control 5V buzzer using mcu and a single 5 V power supply
Triac-Construction and Operation
Circuit Project: Wireless Doorbell
LED sequencer
A Repeating Timer Circuit No.7
Transistor Based Burglar Alarm - Adding Extra Zones
Stepping CS6061A touch dimmer light circuit