Trying to get hold of a few power transistors for a project but having difficulty finding anywhere with some in stock. Normally I order from RS but they have a £5 delivery charge…

Maplin have a selection, but I don’t know enough about transistor terminology to know if they’ll work for me. I’m looking at the TIP31C (needs to be that form factor for cooling). They’re being used to drive LED arrays which have high power requirements (2A each at 12V), switched from a 5V 20mA IC output (via PWM from an Arduino).

To cut a long story short, please can someone who knows what they’re doing read the TIP31C datasheet and tell me whether it will work? I’m currently using BFY51’s but they can’t cope with more than 1A.

I think it’s the base-emitter saturation voltage that’s important – which seems OK to me for the TIP31C – but I could have got the wrong end of the stick over what it refers to.

Sorry for the long-winded question!

would have to be collector-emitter saturation – base-emitter voltage is a normal forward bias 0.7V for all silicon trs. But aren’t bipolar transistors old hat now – what about FETs ??

I’ve had a look at the specs and TIP31C is rated 3A max, which is a smaller margin than I’d be happy with, as that’s usually unrealistically measured with the case held at something like 30°C (ie perfect heatsinking)

simon – thanks very much for the advice. Replaced with 3 MOSFETs and running very nicely now, cases cool to the touch.

Help much appreciated!

Dave.

I’d forgotten I even knew that stuff :o)