Cathode resistor and cap feeding plate of following stage-What's that called?

squarewave said:

It's negative feedback. If the input goes up, ultimately R10 goes up (contributes current) but since it's connected to the cathode it serves to throttle Vgk.

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squarewave said:

It's negative feedback. If the input goes up, ultimately R10 goes up (contributes current) but since it's connected to the cathode it serves to throttle Vgk.

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Mbira said:

I think I understand. When the second stage plate goes up, then that in turn is raising the first stage cathode so the differential between cathode and plate of first stage is less so there is less gain. Is this correct?

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ruffrecords said:

Close but not quite. The tube responds to the potential between its grid and cathode. If this potential increases its plate voltage decreases.  This causes the following tube grid/cathode potential to go down so its plat voltage goes up. R10 therefore raises the voltage at the cathode of the first tube so the potential between the grid and the cathode is reduced. Hence it is negative feedback.

In general, negative feedback is described by how the feedback signal is derived from the output and how it is applied to the input It can be derived from the output current or voltage and it can be applied as an input voltage or current. There are four combinations of these so there are basically four types of negative feedback.

Cheers

ian

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