• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Transistor switch

Status
Not open for further replies.

hantto

Member
Hi, I'm plaing to make a thermal switch, and i want to do it with a transistor (relays click anoyingly) but I'm not sure of what transistor I should use. The voltage throught the transistor will be about 12 volts and the current about 5 amps. Now I'm wondering if anyone could help me, will a normal biopolar (BD243) do the job or would it be better with a fet, or even a mosfet?

Thanks for any explanation! :D
 

Chippie

Member
You could use an Lm311 op amp as a comparator thermistor as your temp detecting device, with something like a 10k resistor as a pull up on the output(its an open collector op amp) and use a BUZ11 mosfet to switch with.....Does that fit the bill ?
 

hantto

Member
Yes, thanks. :) But I have already the temp sensing circuit ready, i only wanted info on the transistors :wink: but thanks for the help!
 

Phasor

Member
A BD243 will do the job, though it's only rated at 6A, so you will be getting quite close to its limit. You may want to consider something a little higher rated (eg, MJE3055 - 10A).

Using a mosfet has advantages and disadvantages. They require very little drive current (several pA into the gate), but tend to have a higher "on" resistance than bipolar transistors. However, if you are prepared to pay more, you can get MOSFETs with a low on resistance.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top