13n50 and 18n50 Mosfets

Have another look at the datasheets, the 13 and 18 refer to I_D (continuous current rating.

R_DS(ON) also varies which may possibly make using the 13n50 (which has an on resistance value about 35% higher than the 18n50) a problem for circuits designed for the 18n50 that require a lower on resistance. General switching circuits should be unaffected by changing from one to the other.

What's the circuit you are substituting parts for?

Hi

its a power supply for a plasma tv. Yes you are right there is a 35% difference in the ID. But would it make a difference in the psu circuit

But would it make a difference in the psu circuit

Possibly, depending on its function in the circuit. Are you trying to replace a 13n50 with a 18n50, because if you are there probably won't be an issue.

Do you have a circuit you could post?

X n Y is a generic N mosfet description. Since we're talking about one of the not too many healthy competition driven industries left, the semiconductor industry, there are manufacturer differences, and you'll have to compare the exact component with what's available to you. And if you have to substitute, especially on resonant cirquits, it can be tricky. Total gate charge and current rise-fall times will not always match, and if for example it's used on uncumped inductance, like on a single switch converter, avalanche characteristics and integrated diode recovery times are also very important. S.M.