[time-nuts] Nuvistors and FETs...

Charles P. Steinmetz charles_steinmetz at lavabit.com
Mon May 3 15:39:13 UTC 2010

Bob wrote:

>Last time I went down that road, finding a FET with *low* enough Gm 
>to match the tube was the issue.

You can always lower the gm of a FET by adding source resistance.  To 
replace pentodes, you can use cascoded FETs (you may or may not be 
able to use the existing screen supply for the cascode gate reference 
-- if not, you'll need to figure out what else to do).

Supertex makes some depletion-mode MOSFETS that have characteristics 
similar to tubes.

Best regards,


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