OP amp with PIC Single Supply

[Ayne]

I want to use TL072 with PIC ADC,
and not want to use any other IC for making a dual supply like Nigel do in his tutorials.
only want to use opamp with single supply, help needed.
Thanks

 

[eng1]

That op amp is not designed for single supply operation and if you use a single supply, the output voltage will always be greater than about 2 V.
If you want to sense voltages near ground you have to choose another op amp.

 

[Ayne]

other opamp, commonly used???

infact in our local market, commonly used parts only available.

 

[art-666]

I used LM324 but you could try looking on Google.com for "single supply op-amp" and try to find local to you (also try for a rail to rail type)

**broken link removed**

Art

 

[Nigel Goodwin]

I want to use TL072 with PIC ADC,
and not want to use any other IC for making a dual supply like Nigel do in his tutorials.
only want to use opamp with single supply, help needed.

The reason I used the other IC to generate the -5V rail is that it makes it a LOT easier - with a single rail IC you have the problem that it might not go 100% down to ground. I also used a 2.5V precision voltage reference, to avoid the opamp needing to go 100% to 5V as well - and it improves accuracy, which is a nice added bonus.

If you want to use a TL072 - then copy my tutorial, it won't work very well otherwise!.

 

[ericgibbs]

hi ayne,

The LM324 is designed specifically to work from a single supply rail.

Also the TS358 dual opa [25pence UK] will accept common mode input signals to Vee/Gnd.

If you are considering any serious work with opa's, low level dc in particular, I would recommend a dual rail supply.

Some of the 'ac' opa circuits with potential divider offsets have some poor features, in particular power rail noise and changes in the gain/frequency performance. To overcome this, additional components, zeners, caps and the like are required.

Its much easier to generate a negative rail voltage.

Regards
EricG

 

[Hero999]

Are you planning to power this from a transformer or mains adaptor?

Get a mains adaptor with an AC output, it's easy to make a dual supply from the output.

Why are you botherd about using another IC to make a negitive supply? Whilst there are better ICs for this a 555 can be used and it's very cheap too.