| Electronics > Beginners |
| Common emitter push-pull? |
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| JS:
--- Quote from: Hero999 on June 23, 2018, 05:17:06 pm --- --- Quote from: JS on June 23, 2018, 12:22:31 am --- --- Quote from: Hero999 on June 22, 2018, 11:53:41 pm ---Just thinking Q3 will be dissipating a fair amount of power. I'm not sure if it's a good idea to drop that kind of voltage and current, even at 50% duty cycle, so a collector resistor is a good idea: I'd go with 22k. Another option is to add 100V zener diode and biasing resistor, so Q3 no longer needs to drop such a high voltage. --- End quote --- Meh.. You need to drop that energy somewhere, expend your money in a zenner or a bigger tranny, I'd go for the single part. JS --- End quote --- I suppose the zener could be replaced with a cheap resistor, but it would still require a high voltage transistor. --- Quote from: JS on June 23, 2018, 03:07:01 am --- --- Quote from: T3sl4co1l on June 23, 2018, 01:16:06 am ---OP hasn't mentioned how much current or capacitance drive is required, so it's impossible to say how much drive the transistors also need. Tim --- End quote --- He used 1k load in the schematics, looks like a lot, 20W to the load but who knows... JS --- End quote --- Are you referring to my schematics? I guessed and a 1k load would not dissipate 20W, but 4.9W, since it's capacitively coupled it would get 70V, not 140V. --- End quote --- Doh! The only part seeing almost the entire 140 volts at full load would be that tranny, but at the vase you would only need a few mA so will only be dissipating a watt or so, no worries, can be done and you need a big tranny anyway to stand the 140V, it could probably be the same as the output one. JS |
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