Well - I had a 16V 1.5A AC adapter (AC output), which I built a rectifier and filter for, and I breadboarded this circuit. I have tried with an NPN BJT (TIP41C) and an N-Channel MOSFET (P16NF06), and although the circuit works fine with both, I have a minimum output voltage of 1.9V. I'm not sure where in the circuit this is coming from. When I measure the voltage with respect to ground at the inverting, non-inverting and output pins of the opamp, I get 1.9V, 0V and 4V for the FET, and 1.9V, 0V and 2.2V for the BJT. Does anyone have any clue?
Thanks
electronwaster
Edit:
I tried an LM358P (dual opamp), and that problem went away, so I guess the 741 isn't so good, or maybe it was a dud.
I applied a .65A load at 15V (I didn't have a 12V zener, so I used a 6.2 + 9.1 for 15.3V regulation), and the output dropped by a whole 200mV, so the load regulation is terrible compared to the simulation - this is where you all say "told ya so!". I didn't expect such a simple circuit to have any really great properties, but I'm excited to have a variable power supply that can go down to 0V with no negative supply :-)