mfahadzia Posted August 17, 2011 Report Share Posted August 17, 2011 Hello, I am using 2SB511 Transistor for switching purpose, applied 5 volts to I/p, and 12V on the Collector , it Energies the relay properly when i signal the Base, but it gets heated really fast, what shoud I do? The source on Collector is 12v, 3Amps.... The ratings on transistors says it can bear upto 5A. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted August 17, 2011 Report Share Posted August 17, 2011 Post a schematic.What's the:Base current?W/oC rating of the heat sink?Switching frequency?And is the load inductive? Quote Link to comment Share on other sites More sharing options...
audioguru Posted August 18, 2011 Report Share Posted August 18, 2011 I could not find a datasheet for the very old 2SB511 PNP Japanese transistor, only a few spec's.Its max continuous collector current is 1.5A so your 3A relay overloads it.-5V on the base? -12V on the collector? Then you are using it as an emitter-follower with a voltage of 6V across it times the 3A in it which is heating of 18W and it will melt.You need a more powerful transistor and use it as a switch, not as an emitter-follower. Use a 6V supply and a 6V relay or use a 12V supply and a 12V relay. Quote Link to comment Share on other sites More sharing options...
login
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.