Re: SSTC 555 timer problem

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jan Wagner by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jwagner-at-cc.hut.fi>


> I am using a 555 time rin 50% duty sycle mode for a small SSTC.It is using a
> 12volt regulated supply and is only outputing about 6.5 volts.Nothing gets
> got, not even the totem pole transistors.Do yall get this same output?Whats
> goin gon here?With the normal 555 astab;e mode with variable duty cycle, i
> get around 10 volts out.Whats up with this 6 volts crap?

Where did you measure the 6V?
Directly at the 555 timer output pin 3?

(if you used this series totem-pole setup thing, 2n3904+2n3906 two times
in series and then additional n-channel and p-channel fets at the end,
then the output is really much lower than 12V. And it won't go down to 0V
either. More like 4V <-> 8V. Or worse. If you replace this mosfet totem
pole with power bipolars the output will be better, maybe 2V<->10V )

> Dont MOSFETs need at least like 7-8 volts to even turn on?Is it possible to
> replace MOSFETs with beefy IGBTs?

Yup, you can. But the maximum frequency possible is lower than with
mosfets.
Yeah and IGTBs have around the same gate voltage requirements as mosfets.

cheers,
 - Jan

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 Jan OH2GHR