How much would a cathode follower drift ?

[00940]

In the following schematic, what kind voltage of drift should I expect at the output over time ?

The output would go into an output transformer that can't stand more than a few mA of DC current and I wonder if I should implement a DC servo (probably a copy of SY's Heretical).

Thanks 🙂

 

[DF96]

It will drift a huge amount. This is because for DC purposes the CF is not a CF at all but common-cathode with cathode bias. Without a DC servo there is little chance of the output ever being near 0V.

A DC CF would be better, but still not good enough if you want accuracy to mA levels.

 

[00940]

Thanks. 🙂

A servo is no big deal after all... it avoids the nightmare of matching a parafeed cap to the output xformer for best frequency response.