F5 power amplifier

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npapp

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Joined 2006
f5 w/Parallel Output IC

I am trying to create my own pcb for the first time and I would appreciate any and all advice or critique of the attached layout. I am laying out a board for an F5 with parallel output trans and no limiting circuit.

I am using free software from express PCB, but is there a better inexpensive program.

Cheers Nick
 

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udailey

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jackinnj

jackinnj

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Joined 2002
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Re: f5 w/Parallel Output IC

npapp said:
I am trying to create my own pcb for the first time and I would appreciate any and all advice or critique of the attached layout. I am laying out a board for an F5 with parallel output trans and no limiting circuit.

I am using free software from express PCB, but is there a better inexpensive program.

Cheers Nick
Click to expand...

When considering a layout, the run from the drain of the JFET's to the gate-stopper resistors, and the run to the MOSFET gates from these resistors should be as short as possible.
 
Sangram

Sangram

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Joined 2002
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Jack, thanks for that tip

However if I was using stripboard, I'd need to connect Q5, R3, R15 and P1 to the junction of Q1 and R13 (I'm assuming short connections are required here too, if they are not it makes life a little simpler). This automatically makes it a pretty long trace (5 -6 holes on a stripboard, the pot will take 2-3). The second condition is more easily fulfilled, I can probably solder R13 directly to the gate.
 
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npapp

Member
Joined 2006
Re: Re: f5 w/Parallel Output IC

jackinnj said:


When considering a layout, the run from the drain of the JFET's to the gate-stopper resistors, and the run to the MOSFET gates from these resistors should be as short as possible.
Click to expand...

Thanks for the advice. Which side of this is most critical, the jfet to gate-stopper or gate-stopper to MOSFET? I think I will most likely only be able to accomplish one side of this recommendation since I am hoping to distribute the MOSFETs further apart on the heatsink.
 
jackinnj

jackinnj

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Joined 2002
tech-diy.com
Re: Re: Re: f5 w/Parallel Output IC

bobodioulasso said:


This does not seem to be the case here

http://www.6moons.com/audioreviews/firstwatt7/f5_2.html
Click to expand...

I will stick to my story. The gate resistor on the MOSFET should be as close as possible to the output device. I can get my F5's to operate into the MHz without problems (yeah, I know that's an abusrdity).
 
Sangram

Sangram

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Joined 2002
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Jack, what about the other end? I can probably get within a few millimeters myself on the gate side, but will be difficult on the drain of Q1. There are at least 4 solder connections to be made on that 'track', and this will make it really tough to get better than 15mm or so, maybe a bit more.
 
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npapp

Member
Joined 2006
I can definitely get shorter traces from the jfet drain to the g-s resistors if I move the jfet further toward the MOSFETs, but this gives me a much longer input trace from R1 to the jfet source. Should I worry about the input trace length? I was trying to keep it as short as possible.

N
 
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