Here is the schematic of the circuit I'm trying to build (source) but I only have an IRF9530N Mosfet; I don't have any NPN transistors at hand.
What would the schematic look like with a MOSFET instead of the NPN?
Electronic – How to replace this NPN transistor with a MOSFET
mosfetnpnschematicstransistors
Related Solutions
You can just use the PMOS, and use a pin switched from output low to high impedance (e.g. input) to switch it on/off:
The 10kΩ resistor holds the FET off when the ON-OFF signal is left floating (i.e. your pin is an input/high impedance)
Then when the pin is driven low, the gate is pulled to ground and the FET turns on. You need to make sure the P-ch MOSFET you use has a suitably low Vgs(th) (turn on voltage threshold - some can be quite high) so you want a "logic level" MOSFET.
Simulation:
This may be a common emitter config but it seems that he's trying to test whether the npn is good or not, sorta like a go - no-go test, which is more like a comparator (saturates the npn). May I suggest a simpler circuit? You dont need two supplies, just a +9V battery. Assuming the LED lights up with ~5mA, you'll get 1.8V to 2V drop across the LED. So the emitter resistor should be 1K, and tie the collector directly to +9V. When the button is pushed, the 100uA or so of base current will be sufficient to make 5mA or so of emitter current. You'll get 5V drop across the 1k, 2v across the LED, and the npn will be in sat. You might want to add a 1M resistor on the base to gnd (to ensure npn is off when button is not pushed).
Best Answer
In answer to your question, this is how your circuit would look if you replaced the bipolar Darlington with a MOSFET:
Notice that an IRF 9530 is not N-channel, it's a P-channel MOSFET, so the supply polarity has been reversed.
This circuit is fraught with problems and is barely suitable for experimentation, but for starters I'd cap-couple the source and the load to the circuit and then work with the biasing and feedback.