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gaetan8888 23rd February 2013 04:02 AM

My line buffer preamp
 
2 Attachment(s)
Hello

I've done, with Ltspice, a line buffer preamp with a gain of 1.4x , any opinions about it ?

Any improvements suggestions ?

I include the schematic and the asc file.

Thank

Bye

Gaetan

abraxalito 23rd February 2013 04:07 AM

Looks a bit too much like an opamp :p Why not try single ended input?

gaetan8888 23rd February 2013 10:09 AM

1 Attachment(s)
Hello

Like that one ?

Bye

Gaetan

abraxalito 23rd February 2013 10:17 AM

Yeah then instead of voltage feedback to the gate, how about current feedback to the source? Then a passive RF filter on the input, series L shunt C?

gaetan8888 23rd February 2013 10:29 AM

Hello

You mean moving it to between R10 and V3 ?

Thank

Bye

Gaetan

abraxalito 23rd February 2013 10:34 AM

Between R10 and J3. J3's source.

gaetan8888 23rd February 2013 10:39 AM

Hello

I've just simulated the circuit with feedback between R10 and J3, the result are very bad.

Thank

Bye

Gaetan

abraxalito 23rd February 2013 10:43 AM

It might be because of the 2nF (C4) capacitor - can't use a capacitor with CFB. Also the value of the feedback resistor probably needs reducing as its critical with CFB, unlike with VFB.

gaetan8888 23rd February 2013 10:49 AM

Hello

Your right, I've take out the capacitor and reduced the feedback resistor by half, but it may need more experiment since the thd is higher at -60db.

Thank

Bye

Gaetan

gaetan8888 23rd February 2013 10:58 AM

1 Attachment(s)
Hello

Here's the asc file of that last circuit with current feedback.

Thank

Bye

Gaaetan


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