"Greg Mayman" wrote to "Mike Ross" (06 Jan 03  08:33:00)
 --- on the topic of "I/F"

 GM> Actually the voltage betwen the gate and the channel. And since
 GM> the channel has the audio on one end and ground on the other in
 GM> an application like this, there is a small amount of audio
 GM> component in the gate-channel voltage, if the gate is fed with
 GM> pure DC. This causes the resistance of the channel to vary during
 GM> the cycle of the audio signal, causing distortion.

 GM> This can be overcome to some extent by adding part of the audio
 GM> signal on the drain to the DC on the gate. The proportion is
 GM> about 50%, but for critical applications the amount of audio is
 GM> adjusted by a potentiometer for minimum distortion.

How does it help? For example say we have an N type JFET, and let's say
the signal at the drain is rising positive. From what I've experimented,
at small signal levels the drain resistance stays pretty much constant.
Adding an extra positive bias to the gate would make the drain
resistance drop so keeping the signal voltage constant? Why would I want
that unless I wanted some compression? Maybe I'm mistaken here however.

 Mike
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