Author Topic: Am I missing a secret - any circuit with an Opamp fails  (Read 716 times)

DiscoVlad

Re: Am I missing a secret - any circuit with an Opamp fails
« Reply #20 on: July 28, 2020, 05:09:11 PM »
I assuming that the floaty unused half of the 4558 isn't actually left unconnected.  (Connect - to OUT and VREF to +.)


Basically this, you need to terminate unused inputs or strange/bad things can happen.

antonis

Re: Am I missing a secret - any circuit with an Opamp fails
« Reply #21 on: July 28, 2020, 05:49:59 PM »
There is no need for 1M resistor grounding unused non-inverting op-amp input..
It can wired directly to Vref or GND (whichever comes closer..)
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

DiscoVlad

Re: Am I missing a secret - any circuit with an Opamp fails
« Reply #22 on: July 29, 2020, 12:51:34 AM »
Agreed, the 1M is optional.

However, ground on this circuit is a supply rail and opamp inputs tied to either side of the supply is bad - it can lead to latchup/excessive current draw/noise/damage to the chip/etc.