Okay, so today I wanted to mess around with MOSFETs, specifically the N-channel and P-channel types. I’ve heard a bit about them but never really got my hands dirty, so I figured, why not?
First, I needed to figure out which one was which. From what I gathered, N-channel MOSFETs need a positive voltage from the gate to the source to turn on, while P-channel MOSFETs need a negative voltage. Seemed simple enough, but I’ve learned that things are rarely as simple as they seem.
I started by grabbing a couple of each type from my parts bin. I made sure to use N-channel and P-channel ones. I hooked up a simple circuit with an N-channel MOSFET first, connecting a power source to the drain and a resistor to the source, with the gate connected to a separate power source. I turned on the power and started increasing the voltage to the gate. Nothing. Right, I needed a positive voltage. So, I switched the polarity, and bam, the current started flowing. It actually worked!
Next, I tried the P-channel MOSFET. This time, I figured I needed a negative voltage, so I connected the gate to the negative terminal of the power source. I turned on the power, and voila, the current flowed again. But when I connected the gate to the positive terminal, the current stopped. It was like magic, but the kind of magic that makes sense after a bit of head-scratching.
After playing around with the basic circuits, I decided to try something a bit more practical. I remembered reading that P-channel MOSFETs are often used for high-side switching, so I set up a circuit where the MOSFET was controlling a load connected to the positive side of the power supply. I used an N-channel MOSFET for this, and it worked like a charm. When I applied a positive voltage to the gate, the load turned on, and when I removed the voltage, it turned off.
- Experiment 1: N-channel Setup
- Hooked up power to the drain.
- Resistor to the source.
- Played with gate voltage – positive worked, negative didn’t.
- Experiment 2: P-channel Setup
- Tried negative voltage to the gate – it worked!
- Positive voltage to the gate stopped the current.
- Experiment 3: High-Side Switching
- Used a P-channel for a high-side switch.
- Controlled a load on the positive side of the power supply.
- Positive gate voltage turned the load on, removing it turned it off.
I did a few more experiments, trying out different voltages and loads. I even tried using both N-channel and P-channel MOSFETs in the same circuit, creating a sort of push-pull configuration. It was a bit tricky to get the voltages right, but when I did, it worked pretty well. The N-channel would turn on when the P-channel was off, and vice versa.
I learned that N-channel MOSFETs are faster than P-channel MOSFETs. Or at least that’s what I read. I couldn’t really measure that in my simple setup, but maybe one day I’ll set up a proper experiment to test that.
By the end of the day, I felt like I had a pretty good grasp of the basics of N-channel and P-channel MOSFETs. I even started thinking about how I could use them in some of my other projects. Maybe I could use a P-channel MOSFET to control the power to a motor, or an N-channel MOSFET to switch an LED on and off. The possibilities seemed endless.
It’s amazing how much you can learn by just messing around with stuff. I mean, I started the day knowing almost nothing about MOSFETs, and now I feel like I could teach a class on them. Okay, maybe not a class, but at least a short tutorial. And it all started with a simple question: what’s the difference between N-channel and P-channel MOSFETs? The answer, as it turns out, is quite a lot, but also not as complicated as I thought it would be.