OP AMP Positive & Negative Current.

Using Arduino General Electronics
#1

Ive ordered a cheap function generator from the internet . It requires both 12 and -12 power rails.

I also have a variable Buck power supply, I was planning on tuning it to 24v using a voltage divider with two resistors to achieve the power rails.

I have seen that an OP AMP draws (dependent on the output) around 4-5mA max on each rail.

I was just questioning whether this setup would work without complications? I was thinking of using 2 1k resistors to achieve 12v to use for the reference.

Here is is the function generator ( I am assming it uses a R2R resistor + summing OPAMP as they usually do). Function Generator

Thank you for your time!

Trev

#2

I was just questioning whether this setup would work without complications? I was thinking of using 2 1k resistors to achieve 12v to use for the reference.

That won't work, because any unbalance in the current draw from either side of 12 V will shift the reference, due to voltage drops in the resistive divider.

You can use a voltage regulator to establish the 12V reference, but it is better to have a dual power supply.

#3

It depends on what you are trying to do. What are you trying to do?

Can the power supply give 4-5mA power output?

The real issue is how much current will be flowing into your virtual ground. This can easily overload your voltage divider resistors. Often in this case, a second opamp is used to decouple the voltage divider and provide an 'active' ground.

#4

By looking at the comments, I guess this solution isn't the best. The idea was to create a single powered opamp circuit used for the function generator. I guess what ill do is use a voltage regulator to bring it down and use it as the reference.

Thank you for your help!

#5

I see it needs THREE supply rails. +5, +12 and -12. Easy to get that from an old computer supply if you don't mind the size.

Wild guess: the 5volt is for the micro. Has to be correct. 12volt rails are for the analogue parts. The output driver etc.

Not very wise to go switch-mode if you value a clean output signal. A small 2x12volt transformer with LM317/LM337/7812/7912/7805 regulator ICs might be better. You must be able to find supply kits/board like that. Leo..

#6