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Cool then I'll order them.
Just so I understand, where do you get the 3.3V from? If 2.4V is max, I thought it should be below 2.4V. Clearly I'm looking at it incorrectly.It will not be a reliable circuit. Vgsth for the 2N7002P is max. 2.4V. @ 25 °C (datasheet, figure 12). Depending on ambient temperature and the specific characterisics of the individual component the transistor may or may not turn on at 2 V.
Operate the PIC at 3.3 V to get a 3.3V output and you are on the safe side.
Or use a level shifter top shift the PIC's output from 2 V to a higher voltage to drive the MOSFET.
Vgsth is the threshold voltage. Vgs needs to be above Vgsth to turn on the mOSFET.If 2.4V is max, I thought it should be below 2.4V.
This voltage neds to be in your system.where do you get the 3.3V from?
Thanks, but I didn't literally mean where it would arise from, just wondering why 3.3 in particular.Vgsth is the threshold voltage. Vgs needs to be above Vgsth to turn on the mOSFET.
This voltage neds to be in your system.
You can use a simple level shifter like this:
View attachment 29422
M1 is your MOSFET. V1 is the 12 V source (I take it you have that in your system?). Note that this circuit is inverting!
Alternatively use a bipolar transistor only, as shown (remove R3 and M1). R2 then is the load you want to drive.
Without knowing what your load is and what you want to achiev, further advice is difficult.
Today 3.3 V have widely replaced the formerly common 5 V as a common voltage for digital systems. Inexpensive and easy to use regulators are available.just wondering why 3.3 in particular.
No way. Vdsmax = 60 V.Do you think this mosfet could withstand a momentary 3kv drain source voltage, for about 1-2μs.? (when off)
I can just put an appropriate TVS diode across the drain-source right? (that's where the spike would be)Today 3.3 V have widely replaced the formerly common 5 V as a common voltage for digital systems. Inexpensive and easy to use regulators are available.
No way. Vdsmax = 60 V.
If you expect such transients, you'll have to limit them using e.g. snubber circuits and/or zener diodes.
Can do. However, this may not be the best solution. While it protects the MOSFET, it will also create large current spikes. Snubber circuits using RCD components work "softer", thereby mitigating possible EMC problems.I can just put an appropriate TVS diode across the drain-source right? (that's where the spike would be)
Okay, and last but not least: What would be the best way to regulate the voltage powering the PIC? Can I just use a zener diode or a voltage regulator. I need something as cheap as possible with as few components as possible, this is for a production circuit. A link to a specific component would really help.Can do. However, this may not be the best solution. While it protects the MOSFET, it will also create large current spikes. Snubber circuits using RCD components work "softer", thereby mitigating possible EMC problems.
So I guess my question ultimately is how should I wire this. Again, this is for a basic flyback converter, I want to charge the primary of the transformer to the maximum amount. There would then be zero voltage on the line from the battery to the transformer, so then the PIC would shut off. How can this be wired so that I have maximum charge on the primary, while still supplying sufficient voltage to the PIC. Also, if I use a higher voltage through the PIC to switch the MOSFET, would more power be wasted? (This is for a low frequency I don't necessarily need fast switching).That pic will run from 2V to 5.5V. If you are putting it from the 12V rail then I would go for a 5V regulator. It will allow you to switch the mosfet faster and turn it on harder.
No. I understand why you might ask that, because it is similar in operation.Highly resistive sounds like skin to me. Are you trying to build a taser?
Bob
The load involves a proprietary commercial product which I am not in the position to disclose in full. This circuit is only similar to a shocking device in the sense that they both involve high voltage. If it is forbidden on this forum to discuss any circuit which involves high voltage then that should be mentioned in the rules. If I wanted to hurt somebody the internet isn't lacking in creative ideas. But what more can I give besides my word, if you choose not to provide any further advice then please close/delete, I nonetheless appreciate the advice given thus-far.Well, if you require 2kV, those mosfets are simply not going to work.
Unless you can tell us the nature of the load then we're really not going to be able to help you any further.
And since you say it is similar in operation to a Taser, you're going to have to be very specific about what you're doing or I will close (and perhaps delete) this thread.