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eng1 said: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 you said, that's fine if GND is within the common mode range. However, in the Maxim note, Vss may be GND, so the divider may be necessary.Optikon said:Why waste resistors for a mid supply divider? Just wire as non inverting unity gain follower with input grounded and output O/C. Works fine.
ikalogic said:when designing pcb as small as possible, sometimes, i use 'unused' inputs to pass copper track right through them...
SYE said:I think this is probably the worst thing you could do for low noise applications, the Maxim app note explains things very nicely.
Ron H said:As you said, that's fine if GND is within the common mode range. However, in the Maxim note, Vss may be GND, so the divider may be necessary.
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.Hero999 said:I normally connect one input to +V and the other to -V and the output to nothing.