I'm in desperate need of help here! No matter what I try, I can't seem to get this working!
I'm trying to drive a signal transistor with PWM on an AVR ATmega32. My PWM signal looks as it's supposed to:
I have it setup so that I can vary the duty cycle of the signal, and my initial thought was, that I would be able to control the amount of current being piped through the transistor. The idea is to use the small signal transistor in conjunction with two MJ15003 power transistors for regulating power in a high current power supply.
The crude schematic looks something like this:
All devices in the circuit share the same ground, but sometimes when I measure the base voltage on the signalling transistor (TIP50) it just sky-rockets above 15V! What is going on!?
The MJ15003's require 5V @ 5A base current, so I figure my signal transistor is too small.