Fri Jan 7 20:12:36 EST 2011
BJT current controlled resistor
Some early Korg synths and also the recent Monotron (follow links
for Monotron schematic) have a Sallen-Key filter with current
controlled resistors implemented by BJTs. Might be a good alternative
to FETs, which have large V_T spread so might need more calibration.
It seems that the problem is that these are all used as AC / small
signal resistors, and rely on the large base current to flow.