Re: Minimising current in unused op amp
- From: John Larkin <jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 04 Jul 2008 12:08:05 -0700
On Fri, 4 Jul 2008 01:20:49 -0700 (PDT), angus.oliver@xxxxxxxxx wrote:
Hi All,
Having found dual op amp packages around a fifth the price of
comparable single packages from online distributors, I think i'll go
for the double.
(BTW, I'm using supply of +16, and ground).
I don't want the unused channel drawing current unnecessarily though,
or bouncing the output around.. - If I tie the non-inverting input to
+3.3V, and have a high resistance feedback resistor to the inverting
input (with no other input to that pin), would that be as good as
anything? I figure the output won't have to 'try' very hard to modify
the voltage of an input pin with no other voltages on it..
Am I right?
Thanks..
Yup, keep it closed-loop, away from the rails. You don't need the
resistor, just connect the output to the IN- input. 3.3 volts on the
IN+ input should be fine for any opamp.
Some, maybe most, opamps draw a lot of extra current if railed, so
don't tie the ni input to V+ or V-/ground. Some will even mess up the
other amp sections if one section is run open-loop.
If you don't have a suitable dummy voltage handy, and the signal isn't
really fast, you can use the extra opamp section as a follower of the
section that you do use; that keeps it happy, too.
John
.
- References:
- Minimising current in unused op amp
- From: angus . oliver
- Minimising current in unused op amp
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