Simple Soft Latch 1

Why a MOSFET with a NPN and not a PNP?

http://everycircuit.com/circuit/6516180297973760 Is a one button on-off configuration. The led and the lamp are just for shoe. Generally the load would replace the lamp

See thats not "simple"

And why would you use a pnp bjt here?

Personal preference. Current operated vs voltage operated components. I merely shared just to show a different configuration

It also flashes whixh might be a good thing or not. If you keep the push button down @ wyo.

@wyoelk, you are right this mix doesn't make a lot sense.

@kiani, right people do forget to test keep holding the push button and are to quickly happy about its circuit. This version wont work as single push button

Any why doesn't a PMOS with an NPN BJT make a lot of sense?

if you have an idea why this makes special sense, we are listening. One can see it as a mixed teansistor technology, but as these transistors appear at different times in history its uncommon to mix them.

Oh so they cant be mixed up because "they appear at different times in history"? Well, MOSFETs make better switches and pass-trannys because they have a really low on-resistance and because they can burn a lot of power. And if you replace the PMOS with a PNP, the circuit will work the same on this simulator, but if you build it on a breadboard, you will never be able to turn off power to the load. I tried it with the 2907a and the 2222a. See the thing is these BJTs have that small amount of leakage current. When the 2907 leaks a bit of current, that goes to the base of the 2222 and the transistor turns on a bit. That allows more base current for the 2907, which turns it on harder. The 2 trannys turn each other on harder and harder an (in a few microseconds, i guess), the load gets its power again. But that doesn't happen with a MOSFET as the pass tranny

Also never a solid plan to mix current operated and voltage operated components as creates circuit imbalance and shortens both components lifespans

I kept the 2222a and used an IRF4905 instead of the 2907

Heres another version. http://everycircuit.com/circuit/6461633978433536

@wyoelk how so?

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