I'm trying to understand why two-BJT transistor-based capacitance multiplier shows bad performance. The circuit (note that capacitance multipliers are bi-polar):
Basic RC elements in all above circuits are 10μF capacitor and 10k resistor.
Red graph was taken from the top pin of R6, blue one from that of R32, green one from that of R1, respectively.
Please ignore the circuit in the bottom left corner, it's unrelated.
Emulated capacitor in op amp curcuit discharged from 10V to 1V over ~2200 secs (36 min), emulated capacitor in BJT circuit did so over ~11 secs, natural one did so over 0.22 secs.
Emulation is apparently correct both in BJT and op amp performance (discharge slopes are exponential in their visible shapes).
Leverages in both emulations are resistor pairs of 10 and 100k Ohms (R3-R4 with R2-R5, R24-R30 with R23-R31 respectively).
Modifying hFE values of the transistors and their emitter resistors gives little effect.
Note that one can enlarge emulated capacitor in both cases by decreasing R3-R4 (R24-R30) and by increasing R2-R5 (R23-R31).
But why do hFE values matter so little here (200 times worse than op amp in any way)?
Did I miss anything?