Hi,
In packages with more than one op-amp, what is the best thing to do with the unused inputs, tie them together, tie them to GND or simply leave them floating
I usually connect the unused op amp as a voltage follower, biasing the non-inverting input with half the supply voltage (any voltage in the common mode range is fine) with a voltage divider.
I usually connect the unused op amp as a voltage follower, biasing the non-inverting input with half the supply voltage (any voltage in the common mode range is fine) with a voltage divider.
As an aside, **broken link removed** has some interesting comments regarding the hazards of tying the noninverting input to hard GND (it's related to power supply sequencing).
You'r right... but it depends on whether you need to save space or noize.. sometimes it would be better to short them to gnd, sometimes it could be better to use them like i do, it depends on the target..
Humm.. yes I suppose. I usually tie the spares off with resistors on all the nodes anyhow in case I want to put it back into service while debugging hardware..
Some op amps have parallel back-to-back diodes across the inputs, e.g AD706. A thorough search could turn up many more. this is not a good general practice. You should always check the datasheet before doing this. I think the diodes are most commonly found in amps with BJT inputs, where the Vbe breakdown voltage is less than the rail-to-rail voltage.
What's the best way to bias it so an op-amp uses very little power?
I suppose it depends on the type of op-amp, a rail-rail op-amp with a class A output stages is best biased either so the output is either +V or -V which is why I made such a suggestion.