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Re: Yet more questions about CCS using DN2540

Posted by danlaudionut (A) on October 13, 2006 at 09:01:00

In Reply to: Yet more questions about CCS using DN2540 posted by Lew on October 13, 2006 at 08:20:02:

Lew

>> Will the "hybrid" cascode...achieve the same goal
>> of reducing or eliminating the capacitance

I would think so.
But I would rather have the CCS on top
that would isolate the SS componants better.

>> are there any special considerations

Yes, you have to match them precisely.
I was thinking of that before then I realized ...
If you have each tube's anode CCS doing EZACTLY 6mA
then you have to have the cathode EXACTLY at 12mA
or the cathode CCS will either be fully on or fully off
All the time !!!!.
Not recommended IMHO.
Better solution would be a center tapped choke
on the anode and the CCS on the anode. IMO

>> placing zeners back to back in order to protect the gate

That only applies when you use a battery of substantial value
in the gate bias circuit see Bas' website on CCS:
http://home.zonnet.nl/horneman/
The battery in the bias reduces the noise level 11.5dB.
If you use a resistor for the bias then zeners are not needed.

DanL

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