• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

LTP with CCS and feedback

Status
Not open for further replies.
A sometimes-used topology involves a LTP with CCS in the tail, but with the addition of feedback from both anodes to the CCS. The earliest example I saw is in Curcio's '89 article in GA for his cascode LTP.

The idea is to further balance the LTP by taking signals from both plates through a summing junction and applying it to modulate the CCS.

Curcio's CCS was a simple 1-transistor affair and presumably not real stiff. That may explain the usefulness of this feedback scheme. However, a modern, very stiff CCS doesn't need any help to balance the LTP. So, would you still use this feedback feature? What for? Increased CMR?

Anyone currently using it, or designing with it, can you comment?
 
Yes, CMR is the big deal. You can improve it in Curcio's circuit by running a battery (or string of batteries, you want 80V or so) between the cathodes of the bottom tubes and the grids of the top tubes. I changed out the bottom tubes for FETs (2N5566), then used a 9V battery between cathodes and grids.
 
Status
Not open for further replies.