I'm trying to come up with a single supply high pass filter that is adjustable from very low (as close to DC as possible) to 5kHz.

I'm trying to use a gyrator-based filter with a 2.5V virtual ground and using a transistor to vary the resistance to the virtual ground and adjust the gain. The problem is that the output resistance of the previous stage of my circuit and the on-resistance of the transistor are creating a voltage divider that kills my signal. I'd prefer to not add more amplification stages since I'm trying to fit the design with a quad op-amp package.

Any ideas?

 

Where is your schematic?
Gyrator based high-pass filter, virtual ground and transistor on-resistance are just a bunch of words, not a circuit.

 

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"Love is wise, hatred is foolish, schematics are essential." -Ron H