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jarys Post subject: VDMOS_LDMOS_parameters[T] Posted: Thu Nov 03,
2005 5:41 pm Lieutenant Joined: Thu Nov 03, 2005 5:34
pm Posts: 2 Location: POLAND I need the papers about parameters
the amplifiers with transistors VDMOS, LDMOS versus temperature.
Is bias control necessarily in amplifier with LDMOS ?? How is
the large influence of temperature on parameters in amplifiers with
transistors LDMOS ?? thanks for information Top
IR Post subject: Posted: Sat Nov 05, 2005 11:36 am
Site Admin Joined: Mon Jun 27, 2005 2:02 pm Posts:
373 Location: Germany Hello again jarys, Welcome to the
magnificent world of RF Power Amplifiers! LDMOS transistors
are sensitive to temperature (As any other active device). When the
temperature increases the Drain current Ids increases too and the output
power level increases with it. So you should provide a negative feedback
in order to reduce the drain current over temperature. This is done
by using a thermistor in the Gate circuit. The thermistor is part of
a voltage divider which reduces the Vgs voltage and by that reduces
the Drain current. Here is a link to a Freescale (Formerly motorola)
which uses this scheme: www.freescale.com/files/rf_if/doc/data_sheet/MRF372.pdf
Should you need more information, please post and I will be keen
to help you! _________________ Best regards, - IR
Posted 11/12/2012
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