Opamp question.

I'd like some guidelines on using opamps with a single 5V to 12V power source. From what I see in the documentation and WEB examples opamps require a double +/- power source. For small home automation projects this is not practical at all.

Would be grateful for pointing me to some tutorial or examples on the subject.

Thank you,

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shabaz over 2 years ago

There's several guides on this. Googling for these terms will land you on two PDF documents:

Single-Supply Op Amp Design Techniques

and

A Single-Supply Op-Amp Circuit Collection
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dang74 over 2 years ago

A lot of op-amps require a negative rail because they can't produce 0V otherwise. Look at the VO, VOUT or Output Voltage Swing entry in the tables in the op-amp datasheet. For instance in the THS4031 data sheet you will see if you supply +/-5V at its rails the resulting maximum output swing is +/-3.4V. Put another way you need 1.6V of headroom or margin on the rails in order to produce your desired voltage. So if you were to connect this opamp's negative power rail to GND you probably couldn't produce a voltage any lower than +1.6V.

There is good news though. Some opamps are considered rail to rail. A rail to rail op-amp doesn't require the margin described earlier in my example. If you want to use a single supply in an opamp I would target rail to rail opamps.
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genebren over 2 years ago in reply to shabaz

These two are my go to references for all things in single-sided Op Amp designs!
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dougw over 2 years ago

A few more resources:

web.mit.edu/6.101/www/reference/op_amps_everyone.pdf

ti.com/lit/an/snla140d/snla140d.pdf?ts=1689123779814&ref_url=https%253A%252F%252Fwww.google.com%252F

ti.com/lit/an/snoa621c/snoa621c.pdf?ts=1689188197473&ref_url=https%253A%252F%252Fwww.google.com%252F
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taifur over 2 years ago

Even you can use very common LM324
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stiriac77 over 2 years ago

Thank you all. Good information. Now I need to experiment.

Any suggestions for a nice behaving OpAmp for a hobbyist?
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