[time-nuts] HP 117/10509a

Randy D. Hunt randy_hunt960 at yahoo.com
Thu Jul 5 16:49:59 UTC 2012


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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