An op-amp is a high-gain amplifier, so if both inputs are tied to the same voltage, then noise will amplified thru the op-amp and cause the output to jump around. As others have said, this can lead to oscillation. Noise is not just what is present at the inputs; it's also inherent in the op-amp itself. Even the pullup or pulldown resistors you use are a source of noise.
By tying the unused output to the inverting input, you have a stable unity-gain amplifier, thanks to the internal compensation. You can then tie the non-inverting input to gnd, vcc, or preferably something inbetween. On Thursday, April 1, 2021 at 12:21:55 PM UTC-7 jrehwin wrote: > > That actually sounds kind of like the old military practice of grounding > unused TTL inputs through a 1k resistor. > > I thought the military practice was to tie unused inputs high (instead of > grounding them) through a resistor: TTL takes less current to pull high > than to pull low. > > - John > > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/3ee71a8e-a9ec-4527-8b9b-b81047ddec5fn%40googlegroups.com.
