Electronic – Build a voltage-controlled voltage source out of discrete components

bjtmosfetprototypingvoltage-source

I'm in a bit of a pickle. I need to build a voltage-controlled voltage source, but I don't have any opamps (or time to order them). I have been working for several hours trying to simulate a circuit in LTSpice that will do the job, with no luck. (BJTs were never intuitive to me, and it's been a while since my circuits class!)

I would really appreciate it if you guys could help me out, and hopefully the next poor schmuck who comes across this type of problem will too.

I need to turn a 0-5V DC signal into a 0-15V (not-necessarily-high-current) source. Here's what I have to play with:

  • all the 1/4 watt resistors one could want
  • a bag of 2N4401 NPN BJTs
  • a bag of 2N4403 PNP BJTs
  • several nameless 60V 30A n-channel MOSFETs
  • various capacitors
  • 24V, 15V, and 5V power rails (avoiding the 15V would be nice, but not nessecary)

Best Answer

Try this

schematic

simulate this circuit – Schematic created using CircuitLab

There are THREE inverting stages in the feedback loop. A huge Cmiller across Q6 is what I suggest (I've no simulator right now). The emitter cap is to boost HF gain so the Cmiller takes effect.

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