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

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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

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He used 1k load in the schematics, looks like a lot, 20W to the load but who knows...

JS



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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.

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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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