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Forums
4hv.org :: Forums :: Tesla Coils
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Audio Modulated SSTC

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EDY19
Wed Feb 15 2006, 12:58AM Print
EDY19 Registered Member #105 Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408
Got my SSTC semi-audio modulated, the only thing is the headphone jack cant supply enough power. How do I go about designing a higher power high impedance amplifier? Right now, I have the headphone jack of the radio connected to a 120:6V transformer in reverse (to step up the voltage), and this is connected directly to the gate and source of the mosfet. I want to bias the mosfet to around 3.5V gate charge, however when i do that, the DC bias flows right through the transformer. If i add a diode to the output of the trafo, the voltage drop lowers the signal even more, so it doesn't work at all. I think I just need a big high impedance amplifier, then i will be set. Any suggestions?
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HV Enthusiast
Wed Feb 15 2006, 01:04AM
HV Enthusiast Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068
You need to have a decoupling capacitor in series between your transformer and the MOSFET.

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EDY19
Wed Feb 15 2006, 01:13AM
EDY19 Registered Member #105 Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408
Gosh, Im retarded. Ill give that a try, why did I only think of a diode? Oh well...
Edit... still doesn't work great, but better than it did before. I think the nature of having to start up and shut off starting from the 555 to the 74hc14 makes the circuit not too great for modulating. Oh well, works great without it.
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HV Enthusiast
Wed Feb 15 2006, 02:18AM
HV Enthusiast Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068
do you have a schematic you can post of your entire circuit???
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EDY19
Wed Feb 15 2006, 02:37AM
EDY19 Registered Member #105 Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408
Link2
is the circuit, except i am using a full bridge. The audio ran through a step up transformer, and connected from the gate through the source with a .1uf capacitor in series. The gate is then biased with a 12V wall wart with a voltage divider comprised of a 20k resistor and a 4.7k to get a voltage of 2.28V (thats what worked best).
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