Hi, my supply voltage is 12V. I don't actually care about the precise gain, but I would like to guarantee hitting the cutoff and saturation regions. My purpose is just to extend the linear region, since normally with a common-emitter amplifier it has a very sharp characteristic. In the end I'm going to have a slow outer digital control loop (that I get for free) acting as a very crappy linear voltage regulator.
I'm trying to do it in only one or two transistors. With only one in common-emitter configuration, I can design it to work for HFE's varying in a wide range, with the linear region proportional to the hfe, but I was wondering if there was a way to get less dependence on HFE by adding another transistor.
Maybe an NMOS is better, because then threshold voltage variations only shift the voltage transfer curve left or right, but the gain and linear region size stays fixed.