On 7/4/2012 11:09 PM, Charles P. Steinmetz wrote:
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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I have a PDF document that covers this for Fetrons. This is from
Teledyne. It shows some of the more common tube replacements with the
circuit and actual device number. Let me know if you would like a copy
and I will sent it to you. Or, maybe a better option would be to upload
it to something like Didiers site. . .
Randy
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