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Old 4th February 2011, 11:07 AM   #21
AndrewT is offline AndrewT  Scotland
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If you go to using a 2sk170 then I think you would be better with a gr grade and preferably towards the low end of 2sk170gr.
A BF862 might also work, but again a low Idss device.

There is a thread on using the BF862 in a low gain low noise amplifier.
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Old 9th May 2011, 07:51 PM   #22
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Hi there does anyone have a layout showing the tilman connected together in a Pedal form with LED and 3pdt switch to use like a stompbox? I have the schematic layout, just need to see how to hookup to everything else Thanksd!
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Old 9th May 2011, 09:48 PM   #23
Fenris is offline Fenris  United States
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If you're not afraid to try something, here's a little circuit with three 2sk170s. It only needs 5 resistors, one capacitor, three JFETs and one LED. Gain is about 2, with plenty of driving current. The LED should be a low brightness type with about a 2v drop. It functions as both a power indicator and as bias for the first JFET. The other two JFETs are a source follower and constant current source. Total current draw is about 13ma. You could probably just knock together this circuit "bugsplat" style in a few minutes to see how well it works.
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Old 22nd September 2011, 05:17 PM   #24
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Default Correction on CS vs. CD gain; FET circuits

Quote:
Originally Posted by JT Hawes View Post
One potential disadvantage of common-source circuits is that they offer no voltage gain. In fact, CS circuits are slightly lossy.
Oops. The above quote requires a small edit. I meant to refer to common-DRAIN circuits (CD). Common-source circuits (CS) can indeed have gain.
I apologize for the confusion.

FET gain depends to some extent on the ratio of the drain and source resistors. (Rd / Rs: The internal resistance and load also alter the gain.) For more gain, decrease the source resistor (Rs) or increase the drain resistor (Rd). There are limits, though: The average current must exceed the minimum Idss spec for the FET. Otherwise, your FET will pinch off, and probably quit amplifying.
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