Circuit Design Question

Discussion in 'General Electronics Chat' started by madhat, Dec 12, 2010.

  1. madhat

    Thread Starter New Member

    Dec 10, 2010
    hi all,

    i have this circuit i have to do, but i can't find the exact inductor value , so i changed in the design to match the components values avalible to me , and here it is the circuit before i made any change


    its a colpitts oscillator[​IMG] circuit, i will change the inductor L1 and capacitors (C1,C2) values to 1 μH and 15pf,15pf , with this new values my calculations gave me the same output result before the change, the question is do i have to change the resistors values and C3 value in the circuit too ? and if so what will be the values .
  2. SgtWookie


    Jul 17, 2007
    The resistors and C3 would be the same, but you're going to get around 32MHz to 35MHz out instead of ~50MHz. Parasitics will be problematic with the low values for C1/C2.

    You can make your own 150nH inductor if you have some AWG-22 magnet wire, using the barrel of a Bic pen for a mandrel; wind on 4 turns so the resulting inductor is about 11/64" long (0.169").

    The previous thread on this subject (now closed) is here:
    Last edited: Dec 12, 2010
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    In previous thread, you were looking at a crystal oscillator.

    How precise and accurate do you need the signal to be? i.e. What tolerance in Mhz, temperature variations, load, etc?