building/buying a +/- 15V PSU for powering Op Amps

Discussion in 'The Projects Forum' started by scotchandy, Nov 13, 2011.

  1. scotchandy

    Thread Starter New Member

    Nov 13, 2011
    Hi, I would like to use some 741 op amps for a project and I saw that they need to have a + and a - power supply. Is there any way that I can either buy a PSU that can do this (if so what would be the correct name for it and where can I get one?) or is it possible to use a regular DC PSU and connect the Negative of it's output to the -15V pins of the op amp?
    My circuit will use the 741 op amp chips in several aplications (non inverting amps, summing amps and impedence buffers etc), im not too sure yet how many i will use...
    For the complete circuit I hope to draw a Max current of no more than 2A (probably quite a bit less but a PSU rated to handle a load of 2A sounds good to me)...there will be a lot of 24V DC motors in the circuit and various other stuff. I will reduce this 24V down to 15V for the 741s but will it be possible to run the 24V DC motor from the same PSU?
    Any advice will be great!! Thanks!
  2. John P

    AAC Fanatic!

    Oct 14, 2008
    I don't know what your circuit really needs to do, but what you've said would make me look at a system running off a single +24V supply. I'd use LM324 quad op amps (that's a cheap low-quality op amp, and I'd be careful not to push it to do things it can't do). If the design truly needed a "ground", I'd generate +12V as a pseudo-ground. To know if that would really work, I'd need to hear more, but it's the way I've done things in the past. Note that to run motors off the same supply as op amps, you can't really be in high-performance territory to begin with.
  3. panic mode

    Senior Member

    Oct 10, 2011
    best option is to just make virtual ground if you need dual power. to isolate opamps from noise, i's also use RC network in both 0 and 24V. they don't need much power and loosing 1-2V for better stability is fair tradeoff.

    since opamps don't take much power, how about small and cheap DC/D converter?
    you can get them in 1, 3, 5 or more watts if you really need to:
  4. wayneh


    Sep 9, 2010
    I recommend an old computer PSU, mostly because you can get one for free and maybe even get paid to remove the old computer. It will have a nice +12 and -12 supply. The -12 supply may not have much current capacity (could be 1A or less), but it will be plenty for any op-amp circuits. The PSU will also have a high-current capacity 5V supply, which is very handy for a lot of hobby circuits.
  5. vicm

    New Member

    Nov 15, 2011
    Simple dual rail supply

    get a Radio shack transformer with a secondary of 12.6vac 300ma
    first set of diodes rectify the AC and the following 2 sets
    drop the voltage from about 16.2v to about 14.8v
    ( with the use of the filter caps (470uf)).
    each diode drops about .7 volts, so 2 will drop under 15v.
    be sure and use the .1 caps to help with noise.
    use also at Opamp if over 4" from power supply..

    hope this helps

  6. Wendy


    Mar 24, 2008
  7. vicm

    New Member

    Nov 15, 2011
    this is better than the half wave I sent, based on the fact that if your
    buying or have access to a 25.2vac secondary xfrm..

    the previous one was with the idea you would use a Wall Wart of about 12vac output. and anyone who plays in electronics always as a few old wall warts laying round.