E
electronman
- Jan 1, 1970
- 0
Basics group,
Thanks again for all your helpful responses last week. Also, I
purchased an old copy of Forest Mims' "Getting Started in Electronics"
for $5.00 and am finding it clear, concise, and fairly easy to
understand. Here are my latest newbie questions.
TRANSISTORS
In experimenting with some of the simple circuits in Mims' book, I
burned out several 5mm round LEDs ... they're cheap ... and I learned
a lot from my mistakes. But I haven't quite figured out how to
determine when I've blown out a transistor. Here are some things I've
learned about transistors by using my digital multimeter.
Transistor HFE Resistance between Base/Emitter
2N2907 312 80,400 ohms
2N2222 170 81,000 ohms
2N3906 156 80,000 ohms
2N3904 170 80,200 ohms
So I'm deducing that all (?) small transistors have a base/emitter or
base/collector resistance of about 80,000 ohms. I've learned that HFE
is a measure of forward gain (what unit of measurement is attached to
HFE?) But this experimentation hasn't helped me to determine if I've
blown out a transistor. What method can I use to determine if a
transistor is bad?
Thanks again for all your helpful responses last week. Also, I
purchased an old copy of Forest Mims' "Getting Started in Electronics"
for $5.00 and am finding it clear, concise, and fairly easy to
understand. Here are my latest newbie questions.
TRANSISTORS
In experimenting with some of the simple circuits in Mims' book, I
burned out several 5mm round LEDs ... they're cheap ... and I learned
a lot from my mistakes. But I haven't quite figured out how to
determine when I've blown out a transistor. Here are some things I've
learned about transistors by using my digital multimeter.
Transistor HFE Resistance between Base/Emitter
2N2907 312 80,400 ohms
2N2222 170 81,000 ohms
2N3906 156 80,000 ohms
2N3904 170 80,200 ohms
So I'm deducing that all (?) small transistors have a base/emitter or
base/collector resistance of about 80,000 ohms. I've learned that HFE
is a measure of forward gain (what unit of measurement is attached to
HFE?) But this experimentation hasn't helped me to determine if I've
blown out a transistor. What method can I use to determine if a
transistor is bad?