CLICK HERE FOR INDEX PAGE

DUAL TRANSISTOR MULTIVIBRATOR CIRCUIT

V. Ryan 2004 - 2009

 

PDF FILE - CLICK HERE FOR PRINTABLE WORKSHEET BASED ON EXERCISE BELOW
   

A multivibrator circuit is a circuit that has identical components arranged on the left and right hand sides. In the case of the example below, the two PNP transistors, the capacitors and the LEDs are the key components. This circuit will trigger itself repeatedly and in this way the LEDs flash alternately.

Increasing the value of the two electrolytic capacitors increases the time each LED remains on/off. The transistors are general PNP type. It is important to protect the LEDs and this is achieved by adding the 680R (or lower if necessary) fixed resistors.

 
 

As the switch is pressed, the capacitors charge up and then discharge. As one capacitor charges the other discharges. As the capacitors discharge, each triggers the base of the transistor it is connected to. This allows current to pass from the collector to the emitter and the LEDs light, alternately.

   

 

PCB VERSION OF THE MULTIVIBRATOR CIRCUIT, WITH ALL COMPONENTS IN POSITION

 

PCB VERSION OF THE MULTIVIBRATOR CIRCUIT, WITH THE OUTLINE OF ALL THE COMPONENTS

   

 

   

QUESTIONS:

1. Name the two most important components in the multivibrator circuit shown above.

2. What would be the effect of increasing the values of both capacitors?

   

CLICK HERE FOR NEXT SHEET ON MULTIVIBRATOR CIRCUITS

   

CLICK HERE FOR ELECTRONICS INDEX PAGE

   
 
Google
 
Web www.technologystudent.com