So I was tinkering with an old amplifier circuit last week and totally fried a component – that smoky smell always means trouble. Pulled out the busted part and scratched my head: “Was this a MOSFET or BJT?” Couldn’t remember the difference anymore.
My backyard MOSFET moment
Dug through my junk box looking for replacements. Found these flat-looking things with metal backs that kept shocking me when I touched them – static electricity just loves those guys! Remembered calling them “MOSFETs” before, so I hooked one up to a 9V battery with some resistors. Weird thing: when I touched the middle pin with my finger, the little LED I connected lit up without any direct wire to the battery. Felt like magic!
- No power flow when I first connected it
- Touched the middle leg – boom! Circuit wakes up
- Works like an electricity gate my finger could control
Then came the BJT disaster
Tried same trick with a different part – this chunky black one with three wires coming out. Wired it just like the first one. Touched the middle pin… nothing. Pushed harder… still darkness. Got frustrated and connected all three pins properly. Suddenly the LED blasted so bright it died instantly! Smelled that burnt plastic horror again. Realized this BJT thing demands constant attention from the battery itself instead of just my finger touch.
Key differences I nailed down:
- MOSFETs are like touchy gates – finger zap starts the party
- BJTs are battery hogs – they drain power just waiting to work
- That heat problem? BJTs turn into mini stoves, MOSFETs stay cooler
Ended up fixing the amp with the right MOSFET. Whole mess taught me: when things need quick on-off switching without cooking themselves, go MOSFET. When you need cheap simple juice control and don’t mind wasted battery, BJT does the job. Still got the scorched BJT on my workbench – best teacher I never wanted!