Handy Dandy Little Circuits #23
Sine Wave Generators

Square Wave Generators

Logic Clocks and Oscillators


To determine the resistance to be used for the LED current, substract 1.7v from supply voltage and divide by the current required in mA .

This circuit is the same as shown above in the Logic Clock but with the supply and LED added. Both IC's can be used and have the same pin connections

Cheapo Oscillator

Would you believe you can build an oscillator with only three components ? Resistor, capacitor and a NPN transistor . It works like a Unijunction transistor .
Not all transistors will respond well to this application but transistors such as the NPN 2N2222 and the likes will readily oscillate with a voltage of 10 volts and higher .
This is an experimental project and fun to work with . Use different types of filtering at the output to see different signal shapes .

Contrary to some offhand opinions these circuits do work . Dig in your junk box for those small signal NPN transistors, when you see them working or hear them they are worth using .Try them with a simple amplifier .

The Original circuit graphic bottom left cannot work , reported a gentleman from Australia and suggested an alternative , below right . After checking my 10 years old records , indeed I realised that the original posted graphic had been wrong all those years.
I then proceeded to test the alternative suggested circuit and could not make it to work at all . I then decided to retest my original "Basic Oscillator" circuit and it did indeed worked great and the results are shwn below .

Wrong graphic
Suggested circuit
Still Does not work

 Pictures are stronger than words

Basic oscillator with C =1uF ,Output = 2.5 Vp/p @855kHz
Audio oscillator with C =1uF ,Output = 3v Vp/p @ 930kHz