[sdiy] Single supply op-amp filter biasing question

[Roman Sowa]

yes, you could, but I would just add the "X" resistor straight to 9V and 
skip 100k trimmer and 22u.
56K in parallel with X is your new value of the first resistor for 
filter calculations so keep that in mind.

To rise bias by about 2V, you need X to be 3.5 times greater than R1 
(let's call that what you have there as 56K). And R1 in parallel with X 
should be 56k.
Now do your math.

Roman

W dniu 2017-05-05 o 16:03, Tom Wiltshire pisze:

> capacitor. But since the signal that I'm trying to retrieve with this
> filter is a DC level, using a capacitor (AKA highpass filter) to
> connect the input doesn't seem feasible. So could I do something like
> this, and how would I calculate the value of X?
>
> http://electricdruid.net/wp-content/uploads/2017/05/SallenKeyFilter.png
>
>  Thanks, Tom
>
>