Hello,
I am trying to replace MRF1K50H with MRFX1K80NR5 and having strange problem. I cannot set idle current at 1A level. I slowly increase bias voltage and when idle current is around 0.8A it starts growing by itself rapidly and can reach very high values. I turn off power to transistor to prevent it from damage.
Bias voltage is stable. What could be causing this?
I know that MRFX1K80NR5 does not have flanges so I carefully attached transistor to copper plate with water cooling (using Liquid Ultra as thermal paste) to make sure it will have adequate cooling. Is there something else I am missing?
Thank you,
Nick NA3M
P.S. Transistors were bought from Mouser.com. I do not see NXP letters on them - just some strange logo.
Solved! Go to Solution.
Sure, the drain current increases because of tha device self heating.
The drain-source current of a power LDMOS device is strongly impacted by temperature. In Class AB and for a given VGS, the IDQ rises with temperature.
MRFX1K80H datasheet Figure 3 provides graphs of normalized VGS versus Quiescent Current and Case Temperature.
Also, below are the curves I obtained using the MRFX1K80H model for ADS.
Useful documents on the topic:
https://www.nxp.com/docs/en/application-note/AN1977.pdf
https://www.nxp.com/docs/en/application-note/AN1643.pdf
Best Regards
Pavel
NXP CAS
Sure, the drain current increases because of tha device self heating.
The drain-source current of a power LDMOS device is strongly impacted by temperature. In Class AB and for a given VGS, the IDQ rises with temperature.
MRFX1K80H datasheet Figure 3 provides graphs of normalized VGS versus Quiescent Current and Case Temperature.
Also, below are the curves I obtained using the MRFX1K80H model for ADS.
Useful documents on the topic:
https://www.nxp.com/docs/en/application-note/AN1977.pdf
https://www.nxp.com/docs/en/application-note/AN1643.pdf
Best Regards
Pavel
NXP CAS