The Amp Bias Controversy

[ppppenguin]

There may be a misunderstanding of what is meant by "grid bias". My understanding, which I think is correct, is that it is the DC potential, usually in the absence of signal**. As Terry has said, it is measured between the grid and cathode. This is never positive in any design I've ever seen. In some designs, notably high power output stages, the +ve peaks of the signal may drive the grid positive with respect to the cathode and hence cause grid current to flow for short periods.

**As Terry said, itis possible for the signal to be rectified and affect the bias.