- 2004-03-12 8:42 am
Herewith I declare Nelson Pass guilty for drying up the Toshiba J-FET market by proposing power amps which use those!
As we have to save those complementary Toshiba J-FET's (they seem to dry out earlier than crude oil fields....) I thought of a different input for the F4.
OK, it needs 4 MOS-FET's, so...nothing for resource savers.
Match M1/M3 and M2/M4 for Vgs, take into account that the input resistance is only around 2.5k (who has such girlie preamps which cannot drive this load??) and there you are (hopefully).
PS: to increase input Z you could always replace R1 and R2 with current sources, or raise the front-end supply voltage and use higher value resistors.
PS2: no, the different Vgs multiplier than in the original F4 (TL431) has nothing to do with my proposal...