Quote:
Originally Posted by davepl
That page is a little deep for me, but it's in the right direction. But it's kinda written for people that already know the answer, I think:
"When we operate transistor as the class A common emitter amplifier usually we choose to bias the transistor (apply voltage on VBE and VCE) in such a way (Q-Point) that IC and VCE (output) will swing to its maximum or minimum value without any distortion (swing into the saturation or cut-off region) when the IB (input) swing to its maximum or minimum value"
So that's about where I got lost! But I understand in principle what is happening I think!
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"When we operate transistor as the class A common emitter amplifier..." blah blah blah, that big phrase is noise in the article, because what we are more interested in is the
next phrase "but when we operate the transistor as switch...."
What he's saying is when we use the transistor as a switch we want to turn it all the way on or all the way off.
Quote:
Originally Posted by davepl
I'm not really clear on why the diode is needed for inductive loads. Is it because when the inductive field collapses it shoots a voltage spike into the circuit or something? I don't know anything about inductance, unfortunately.
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I think you got it right. When you power an inductive device and then cut off the power to it, it sends a voltage spike in the opposite direction from normal current flow. So the diode absorbs that by essentially shorting across the coil contacts instead of letting the charge go through the transistor. Inductive devices are things with coils, such as relays, solenoids, and motors.
Incidentally, I noticed my truck has a diode across the terminals that attach to the A/C compressor clutch. That would be to reduce or eliminate sparks across the contacts on the compressor switch when it disengages.