Author: SamDate: 17:03 08-04-07
|
|
hey,
i'm using a LM324 opamp configured as a diff amp. the inputs come
from opamp followers, so there shouldn't be any loading issues.
when i vary the input connected to the inverting (-) terminal
everything's fine - i see a clear change in the differential output.
but when i vary the input connected to the non-inverting (+) terminal
there's no change in the output. any ideas? (fyi, diff gain is
currently 4.7 [470s over 100s])
thanks so much!,
sam
|
|
|
|
Author: EeyoreDate: 17:20 08-04-07
|
|
Sam wrote:
> i'm using a LM324 opamp configured as a diff amp. the inputs come
> from opamp followers, so there shouldn't be any loading issues.
>
> when i vary the input connected to the inverting (-) terminal
> everything's fine - i see a clear change in the differential output.
> but when i vary the input connected to the non-inverting (+) terminal
> there's no change in the output. any ideas? (fyi, diff gain is
> currently 4.7 [470s over 100s])
How about posting a circuit diagram so as to check it's right ?
Are any inputs close in voltage to the power supply voltages btw ?
Graham
|
|
|
|
Author: SamDate: 17:52 08-04-07
|
|
> Are any inputs close in voltage to the power supply voltages btw ?
>
> Graham
yep - i forgot to use a split supply, so it was trying to drive the
output below 0 when there was no way that was possible! thanks!
-sam
|
|
|
|
Author: EeyoreDate: 18:08 08-04-07
|
|
Sam wrote:
> > Are any inputs close in voltage to the power supply voltages btw ?
>
> yep - i forgot to use a split supply, so it was trying to drive the
> output below 0 when there was no way that was possible! thanks!
It's nice when there's a simple answer ! ;~)
Graham
|
|
|
|
1 |
