Transistor - Saw Tooth Generator

Hei Guys,

I have recently started fiddling around my old electronic stuffs, On seeing few transistors laying around an old Sawtooth generator circuit came to my mind. Just felt like posting it, so that it could help any individual who is reading this now... Yeah, I am talking about you... :)

Ok here is the circuit which has uses very simple components like,

BC547 (npn transistor)

BC557 (pnp transistor)

Resistors

and a Capacitor , yup thats about it....

There are actually three blocks to be seen individually and then viewed altogether to understand the working of this tiny sawtooth generator...

First the potential dividers that provide sufficient voltage level to keep the transistors Q1 and Q2 always at ON stage.

Note that the Q1 is a pnp BC557 transistor where as Q3 is the a npn BC547 transistor....

BC557 acts as a current source where as BC547 acts as a current sink.

Here as you see the transistors Q2 and Q3 acts as a pulling down block

The Following picture shows where the sawtooth wave can be seen and where the pulled down spike is given to the base of Q2 which rapidly pulls the voltage across the C1 fall correspondingly, thereby generating sawtooth voltage ..