I am using a bipolar supply with an inverting op amp. The input is a sine wave (5 V p-p) and its frequency can be as low as 10 Hz. I'd like to add a cap to eliminate the DC offset of the sine wave. The input resistance is 10 kohm.
I could change this value and use a 1 uF non polarized capacitor... instead (and this is the question) if I add a 22uF elec. cap, how should it be oriented?
Thanks
EDIT: the sine wave swings between -2.5 and +2.5 V.
As it's a bi-polar supply, and a zero referenced signal, there should be no polarising voltage across the capacitor - so either way should be fine, although it's preferable to arrange for a polarising voltage across electrolytics.
It's a simple voltage inverter. R1 = 10k ohm. The input signal is a sine wave swinging from -2.5V to 2.5V ideally, fmin=10 Hz. I need a high value for C, without changing R1, so I must use an elec. cap.
After your answer I was asked to post a schematic.
BTW this is an input stage and I don't know if other people will apply a zero referenced sine wave as I do... I didn't write this thought.
If I add two diodes (without R2) in the feed-back path to make a zero crossing detector, any DC offset (small or large) is unwanted.
If I can't predict the polarity of the DC offset, do I need to use a non polarized capacitor?
Since you want to capacitor-couple the input, then why is the input impedance so low as 10k ohms which requires an electrolytic capacitor for good low frequency response?
The opamp has an extremely high input impedance with the FETs on its inputs, so use 100k or 1M rersistors. Then you can use a film non-polarized coupling capacitor with a lower value but still have good low frequency response.