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Can current flow in both directions through a JFET channel?

I am beginning to study JFETs . I want to limit this discussion to N channel JFETs and when I talk about current flow I mean conventional current flow.

Most of the sources that I have been studying use example where the gate-source junction is reversed biased and the voltage at the drain is positive with respect to the source and current flows from drain to source.

What if the gate-source junction is still reversed biased and the voltage at the drain is negative with respect to the source. Will current now flow from the source to the drain?

I have also read somewhere that on "some" JFETs, the source and drain connections are interchangeable while on others they are not. Is this true? If so, how do you know which ones will do this?

Any help would be greatly appreciated. Thanks

Reply to
jalbers
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Your answers are there. Scroll down and you'll see "Analog Switch"

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Reply to
Jamie

The answer is YES, at least up to a point since if you go too far it starts distorting and I'm not interested past that point.

Think of it vaguely as a voltage controlled resistor.

Graham

Reply to
Eeyore

That is a good app note. I have used JFETs (2N3819) in audio amplifiers I made around 1970, and also as a voltage controlled resistance in a programmable gain amplifier in a product I designed in the early 1980s. This particular device is still available and can be very useful. I'm fairly sure that the source and drain can be reversed, especially in low signal level applications.

Another good app note, from Motorola, is:

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Paul

Reply to
Paul E. Schoen

That's true of many jfet devices in fact.

Graham

Reply to
Eeyore

That's a very interesting PDF, I just briefly looked it over and there is an assert on a subject that I had an argument once, with one of my colleague's at work.. Not that it means anything now but I think it'll be interesting to see the look on his face when he reads it because I lost that battle with lack of documentation to back it up and since he's the senior man, he didn't need any documentation :);.

Thanks.

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Reply to
Jamie

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