[time-nuts] HP 117/10509a

[Charles P. Steinmetz]

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