Hi, I am using op amps with a single 5V supply. I would like to create a Vcom supply at 2.5V. Is there a recommended way to have a high quality half supply referenced from the 5V supply?

 

Hi, I am using op amps with a single 5V supply. I would like to create a Vcom supply at 2.5V. Is there a recommended way to have a high quality half supply referenced from the 5V supply?

Yes, use another op Amp to make a follower (output directly connected to inverting input) and reference the non-inverting input to 1/2 supply with a pair of resistors. You can add a one (0.1 uF) capacitor from ground to the output of the follower and another capacitor from ground to non-inverting input (0.01uF) for added stability.

If you are using a dual op amp, you can just use one of the the amplifiers to make the 2.5v reference.

Here is some good background reading. Make sure you do not exceed the op amps current rating on this reference (30 mA is common, check the datasheet)

http://www.swarthmore.edu/NatSci/echeeve1/Ref/SingleSupply/SingleSupply.html

 

Yes, use another op Amp to make a follower (output directly connected to inverting input) and reference the non-inverting input to 1/2 supply with a pair of resistors. You can add a one (0.1 uF) capacitor from ground to the output of the follower and another capacitor from ground to non-inverting input (0.01uF) for added stability.
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Note that some op amps can oscillate with a capacitive load. You may have to add a small resistor in series with the op amp output and any added output capacitor to insure stability.

 

[snip] do not exceed the op amps current rating on this reference (30 mA is common, check the datasheet)

20mA is safer. If you need more current, you can drive an NPN transistor from the OP AMP. If you're not using a rail to rail OA, you won't have much head room.

 

TLE2426 is a precision virtual ground for creating a slit supply.

 

Hi MrChips,

TLE2426 is a precision virtual ground for creating a slit supply.

Neat idea. Albeit, not one that I'd be inclined to use...

 

Hi, I am using op amps with a single 5V supply. I would like to create a Vcom supply at 2.5V. Is there a recommended way to have a high quality half supply referenced from the 5V supply?

You could use TI TLE2426, it will track the supply and give a half rail, I've used it a lot...Peter