Makes perfect sense. Thank you. So far I've used op amps for a few
simple things but still need lots of study and practice to become more
proficient with them.
To date my experience with op amps has all been cookie-cutter cookbook
applications. They work, but much more study is required. At least I now
know a little more
about the proper way to tie off the unused ones. Thanks. -Chuck
---- Original Message ----
From: "gregebert" <[email protected]>
Sent: 4/1/2021 7:36:20 PM
To: "neonixie-l" <[email protected]>
Subject: Re: [neonixie-l] LM-324 op amp
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
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