Regenerative Amplifier control

Discussion in 'General Electronics Chat' started by Bench Fire 3000, Jan 10, 2009.

  1. Bench Fire 3000

    Thread Starter New Member

    Jan 10, 2009
    Hello, I am a newbe here and hope some one can point me in the right direction as I can't seem to find much information on how to control a Regenerative amplifier. I know they are hard to keep on a set frequency due to being unstable because of using positive feedback. I can keep the circuit stable using a open loop arrangement through the use of a external signal generator, but would like something more simple and self contained. Internal to it's self.

    What I am doing is using two power transistors, where the first one triggers the second one, the output of the second one is connected to the secondary (8 ohm) of a audio output transformer, and also to a cap, then to the base of the first transistor. This set up oscillates more less @ 5000 times per second. The primary side of the audio output transformer (1200 ohm) using this arrangement, has a 300+ volt "spike" output that is then fed to a voltage multiplier circuit that produces a 6000 volt DC pulse. It is a very simple but effective setup that produces a very sharp HV DC spark @ more less 5000 impulses per second.

    The second transistor output is short circuited through the 8 ohm secondary of the audio output transformer @ 5000 time per second.
    This is what causes the sharp 300+ volt spike in the primary side of the transformer.
    The audio output transformer is wired in the reverse of normal.

    The arrangement works "ok" but is subject to drift due to being powered from a 9 volt battery, plus loads on the output seem to cause frequency drift as well. I know that complex control systems could be used to maintain frequency control, but I was looking for something simple, stable, adjustable, compact.

    Bench Fire 3000
  2. flat5

    Active Member

    Nov 13, 2008
    It drifts because of loading on the transformer.
    I would try using a buffer stage to isolate the oscillator and the transformer. You will have to completely change your circuit to do this.