[time-nuts] HP 117/10509a
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Thu Jul 5 06:09:44 UTC 2012
Don wrote:
>the fet breakdown voltage has of course got to be high enough.
If the nuvistor is used as a common-cathode or common-grid amplifier,
you can cascode the fet with a bipolar to extend its drain voltage
range. You will need to come up with an appropriate bias source for
the bipolar. Generally, you would want at least 10-15 volts across
the FET channel.
Choose an appropriate JFET (transconductance, drain current, and
gate-drain voltage similar to the nuvistor at the nuvistor's
operating point). You can add degeneration (source resistance) to
lower the FET's transconductance if it is higher than the nuvistor's.
Best regards,
Charles
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