View Full Version : Transistors/Diodes

October 11th, 2007, 01:10 PM
Can anyone give me the values/codes for bog standard npn transistors and silicon diodes for multipurpose and general tinkering? Transistors would probably be used for switching rather than amplification (Does that sound right? ;) )

At the mo in college I'm doing basic 555 timer circuits, we've just finishing astable and monostables. Pretty easy so far, it's the theory that's tricky! I like to do everything at home on my own from memory, helps it sink in. Got plenty of resistors/caps and a basic experimenting bench but hardly and transistors or diodes, Hence this thread. Maplin item codes would be nice too :)


nige the hippy
October 11th, 2007, 01:47 PM
Hello you're back!
Small GP NPN transistor - BC548 (300mA max, about 30V breakdown (although I used one at 120V deliberately once!) and current gain of about 250 off the top of my head)
For higher power & darlington pairs the TIPxxx series are pretty good.

Signal/switching diode - 1N4148 (100 mA max (again off the top of my head))
Rectifier diode - 1N4001.. 1N4007 (1A max, & the 4007 will stand 1KV reverse)

Actually if you check out the components page on the maplin website, they're kind-of listed as general purpose this and that...

Don't be lazy!;-)

October 12th, 2007, 01:34 AM
While we're onto the subject, would 1N4151 in most cases be a suitable replacement for 1N4148? I searched a bit on the characteristics, but didn't come to any conclusion. The thing is that I've bought a few bags of random surplus components, and got a heyload of 4151's but exactly one 4148.

nige the hippy
October 14th, 2007, 02:15 AM
For "normal" frequencies, all you really need to worry about is not exceeding the max repetitive reverse voltage (Vrrm) or the max forward current. If you're using the diodes for signals (i.e. not using them as a power rectifier, or charging HUGE capacitors with them) & at less than 75V (!) you should be ok with either.

October 14th, 2007, 08:30 AM
Right ho, thanks for the advice!
Will get round to it when I get some money...Currently job searching :(