Power booster : tips for decreasing noise

Discussion in 'General Electronics Chat' started by Bobbylabidouille, Nov 16, 2014.

  1. Bobbylabidouille

    Thread Starter New Member

    Nov 16, 2014
    Hello everybody, here my first post!

    I have a problem with an analogic circuit. This circuit works but, while working, it creates too much noise ... I would be glad to get some tips in order to improve it!

    The input signal is a potential sweeping from 0 to 5 V (NI-6009). This potential is applied on a load (Resistance, electrochemical cell etc...) and then current is recorded through a resistance. The circuit helps the NI-6009 to sustain power in the range of 0,5 W to 1 W.


    I carried out experiments with a 10 Ohm-load, I obtain standard deviation of the input signal of ~ 100 mV and the aim would be, if possible, 10 mV.

    I managed to reduce the standard deviation to 60 mV in inserting capacitors between the bases and the emitters of the transistors, but I don't really know what to do...it is above my competencies...

    Does someone know what I should insert and where in the schematic above?

    Many thanks by advance!
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    Biasing the transistors would probably help. At the moment, your amplifiers will go open-loop every time the output crosses the zero point.
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Put some large caps across your four power supply sources (2 x 5v and 2 x 12v).

    Also, TI advertises the tL 071 as a low noise version of the tL081. Both are fairly old. Newer, lower noise op amps with the same pin-out are a ail able from TI.
  4. ronv

    AAC Fanatic!

    Nov 12, 2008
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Feedback cures all if his transistions are slow enough, oops, he has a noise issue - time for a better amp design.
    This is a good option - middle option in RonV's link.