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op amps

NickMikhayNickMikhay Posts: 41
in PASM/Spin (P1)

if anyone has worked with lab power supplies, since I am thinking of building one that is op- amp friendly
what I would like to know is when you turn the knob to adjust voltage on the positive rail its clockwise to increase, right?

but on the negative rail is it clockwise to decrease, in other words as you turn the dial the output voltage gets more negative with respect to ground and magnitude increases.

which way should you turn?

I know not really prop related but thought it wouldn’t hurt to try. Which way would you prefer?

Comments

  • evanhevanh Posts: 15,915
    edited 2022-05-03 01:16

    Sure, but not usually something that is encounter in practice. A split rail output for op-amps is usually a single adjustment, if adjustable at all. Mostly just have such as a fixed low-current auxiliary output.
    When a lab power supply is designed with two adjustable voltages, the two associated outputs are usually isolated from each other. They can be switched between independent, slave-paralleled, or slave-seriesed. Slave-seriesed would produce the same config as the fixed auxiliary output.

  • frank freedmanfrank freedman Posts: 1,983
    edited 2022-11-04 04:56

    If you are building a lab supply for your own learning experience go for it. But there are so many on ebay and third party equipment sales/salvage sites so they may be a better choice as far as cost and time goes. Also depending on what you build, the supply could be to noisy (ripple, switching noise, etc) for you use. Some power OpAmps can handle greater than two amp output.

    As to the knobology, tracking supplies will increase clockwise and the negative equal and opposite. When not tracking, still the same direction. In other words, ignore the sign, clockwise increases the magnitude counterclockwise decreases magnitude.

    For use, you would tie the negative of the positive rail supply to the positive side of the negative power rail. This tie point becomes the common (0v) reference. Can be jumperd to earth ground if you want.

    One of the best sources for opamp info is TI. They also sell a great learning lab made for them by MikroElectronica. Here is a link:https://university.ti.com/en/faculty/teaching-materials-and-classroom-resources/ti-based-teaching-kits-for-analog-and-power-design/analog-system-lab-kit-pro

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