Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Sawtooth wave generator

  1. Jan 6, 2012 #1
    http://pokit.org/get/f118bc654187e429ec1bb489e1eb3a38.jpg [Broken]

    Suppose we have a sawtooth wave generator, like in the picture.

    I have a fairly simple question:

    If lets say Vcc is 15V, and lets say voltage drop across Re is 2.7V, and saturation point of Uce is 0,2 V.

    Provided that the period between impulses are long enough, what will happen when capacitor is full? Transistor will go into saturation right?

    Or another way to put it, will my MAXIMUM(allowed) amplitude, or voltage across the capacitor be:

    15-2.7-0.2=12.1 V?

    And I can choose my amplitude by adjusting the frequency of those impulses?
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Jan 6, 2012 #2


    User Avatar
    Science Advisor

    Yes, that is right.

    That is not how this circuit would normally be used, though.

    Ideally, the lower transistor's base would get a new pulse to discharge the capacitor just before the sawtooth wave reached maximum amplitude.

    If you wanted to use a different frequency, then you would adjust R1 to give a different charging rate for the capacitor.
  4. Jan 6, 2012 #3
    Understood. Thank you. Needed somebody to confirm my thoughts.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook