Op Amp Vref almost Equal to Supply +V Will it atill work???

[bluelagoon]

If my Vref on the opamps is close to almost = same voltage as the Supply +Voltage, will my opamps still function,

I have + voltage supply at +8.7V on my opamps and a Vref Voltage of +7.15V, and I am getting no output, a lot of amplified Hiss but no sound.
Is this because the bias on the opamps is way off, ?? I am assuming as much, just need more enlightenment.
Thankyou.

[PRR]

+ voltage supply at +8.7V on my opamps and a Vref Voltage of +7.15V, and I am getting no output,

You are a bird. You flap your wings. A big bird with big wings.


If you get into a 8.7 foot high garage, with your body at 7.15 feet, you have almost NO room to flap. Your up-flap hits the ceiling. About 1.5 feet, and 1.5 Volts is about the dead-zone of an opamp from its rail.

You might expect a SLAP SLAP SLAP on very loud/large flapping, large enough to clear the ceiling momentarily.

May be good to know why your Vref is 7.15V.

[bluelagoon]

Thanks for your reply, I found the problem, It was after amending the LED power supply,  I had to cut the Ground leg of the LED brightness pot, and in the process messed up the ground supply leg of the virtual ground bias resistor.
Fixed that, and all voltages back as expected. Cheers

[bluelagoon]

By the way, that is one big bird that Argentavis magnificens. Wouldn't want to be pooped on from above by him.

[R.G.]

The headroom issue is big, as noted. There's another issue.

Some opamps can't stand their inputs being too close to the power supplies. There is a number listed on the datasheet of nearly all opamp chips detailing the input common mode range. The opamp may not work at all or may have ugly results like banging the output to the opposite rail than expected if the inputs get out of the common mode range.

Generally this was a problem in single power supply applications, where ground was the negative power supply and the application wanted the + input to be held at zero/ground too. So-called single supply specialized opamps have an input common mode range that includes the negative supply for proper function. "Rail to rail" inputs can work without ugly behavior other than banging the output into the power supply without the phase inversion of non-rail-to-rail opamps.

Look up your actual opamps and see what their input common mode range is.