Created by
Created March 28, 2012
Last modified March 28, 2012
Tags bjt   power   pwm  


Power BJTs can be used to switch lots of current, but they require lots of base current as well.


In response to

V2, R2, Q1 model the square-wave-switched optocoupler.

Q2 needs R3 or else it will draw ridiculous base currents.

Q3 needs R4 or else it will similarly draw ridiculous base current. (Though it does need quite substantial base current in this case!)

Try running the DC and Time-domain simulations. Switching times seem to be in the tens-of-microseconds range, not the 0.5ms discussed in the original post.


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