We have purchased 10 qty of STL160NS3LLH7 MOSFET IC. We found that Drain to source impedance of MOSFETs is varying( NOTE : MOSFET were not connected to any external circuitry while measuring impedance using DMM). For some of the MOSFETs it was around 1kOhm for others it was 2kOhm and 3kOhm also. I am not getting same performance with all the MOSFETs. I think that this because of this variation in Drain to source impedance. I have never seen such a peculiar behavior of MOSFETs. Is it a manufacturing problem or these MOSFETs behave like this only? Please explain!