fet with 4 terminals

I have designed a mixer in which the LO is fed at the source. the simulation results are fine but the problem is the actual FET device contains 4 terminals i.e. 2 source terminals...now if i apply LO to one source terminal and ground the opposite source then the transistor blows up the moment I apply the LO..so I dnt knw wat to do with the other source terminal...I cnt change the design now so applying the LO at the gate using a combiner is not an option..any help would be appreciated..thnx

How do you know, that the device has "2 source terminals"? Have you seen a datasheet?

probably I should have been clearer..yes I have the datasheet and also I have fabricated in microstrip ...the device has 4 terminals...and have tried grounding the other source terminal but the transistor blows up...my question is...am I doing it right wen I apply LO to one source and ground the other source terminal...if not wat do I do with the other source terminal..where does that lead go?

Just cut one off, very close to the package body, and you are all set. They are connected together inside of the package, thru wirebonds to the chip's source.

thnx fr the reply....but cutting the other source off...is it really not gng to cause any problems? Is tht the reason u thnk the transistor is blowing up? will try it tomorrow...and thnx again fr the reply..

if both source leads are connected together, and you are grounding one, you are then also grounding the other, and you can not then use the source for your LO port.

You do not explain your circuit, but I am assuming that the fet "blows up" when some DC bias voltages are present. By grounding the source, are you violating the absolute maximum voltages or currents allowed?

thnx fr the reply..actually the problem occurs the moment I apply the LO at the source...bfre tht the transistor is fine..

You mean there is no dc bias?

no...I mean of course there is a DC bias but the currents shown are fine from the dc bias...I measured the drain current...its fine...but on the application of LO at the source the transistor blows out I guess... coz thn all of a sudden the drain current increases by a huge amount...and all the terminals of the transistor show a short circuit between thm...

thnx a lot...u suggestion really helped.