F4 power amplifier

[veteran]

Not yet, but I will probably order few to make sure, that there are no mistakes (schematic and layout is very easy so there shouldn't be any surprises). I have 200mm high heat-sinks and they will feat just fine

If somebody want to have less problems with matching FETs - IRFP240/IRFP9140 should work better in output stage (I was using such pairs in Dracula amplifier). I added RA,RB and CA, CB components on this PCB but they can be skiped (just place jumper instead of RA and RB).

3D view of this board:

[mpmarino]

Thanks for sharing veteran,

I don't know if the day will come that I can do a nice layout. I have had a couple of successes but Maybe someday I'll have something worth sharing

Jacco and Choky... be quiet!

[Zen Mod]

Originally posted by mpmarino
.........................

Jacco and Choky... be quiet!

why ?
we always behave..........

[mpmarino]

Originally posted by Zen Mod



why ?
we always behave..........

Right.....


Hey, would it be a big deal if the ZENERS were 6.2v as a sub for the 6.8v in the circuit?

Oh, are Jfets wicked static sensitive?

[Zen Mod]

Originally posted by mpmarino



Right.....


Hey, would it be a big deal if the ZENERS were 6.2v as a sub for the 6.8v in the circuit?

Oh, are Jfets wicked static sensitive?

you mean crippled 2N4736.......

they're there just for protection- just put what you have in drawer or don't put anything if you are confident that you wouldn't have short circ between headphones during connecting cables to amp

[mpmarino]

you mean crippled 2N4736.......

right...



... and thanks.

The ZENERS look to be there to protect the OP FETs, right? Is it not necessary to protect the Jfets? Aren't those little buggers fragile?

fragile : (fra-geel-ae) 1. made in italy

[Babowana]

Originally posted by mpmarino


The ZENERS look to be there to protect the OP FETs, right? Is it not necessary to protect the Jfets? Aren't those little buggers fragile?

fragile : (fra-geel-ae) 1. made in italy

When we adjust bias voltage, e.g. TL431, we could make a
mistake by accident. If the bias voltage is too high,
the power mosfets would suffer from excessive current.
If so, when we have no spare parts, hmm . . .

Meanwhile, the input jfets are formed with self bias. As long as
the rail voltages are under control, the jfets are safe. In my
opinion, the probability for us to use wrong rail voltages are
ignorably low.

[Zen Mod]

Originally posted by mpmarino

.................. Aren't those little buggers fragile?

fragile : (fra-geel-ae) 1. made in italy

not like m-fets
you don't need gate protection for them,except maybe few dozen ohms in line with gate................for radio freq



fragile?
krhki,you mean?

[mpmarino]

Thanks Choky

I appreciate it.



hot off the presses:

[twitchie]

My first etching

Thanks to Nelson Pass for sharing the schematic

Thanks to Veteran for sharing the layout

Thanks to Tom Gootee for the 'how to etch' instructions