I was symulating some RC filtering before I have made a board but results were bit worse with filtering, the supply rails are reference for driving the mosfets here so with filtering this ''reference'' would be different for part before RC and after RC filter. In spice symulations it was a bit worse anyway.
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Rubbish.
I just went up and dismantled the 150 so that I could access the underside of the PCB.
The V+ trace is directly connected to the nearest Source Pin and via a short trace to the further Source Pin. The V- is similar, just slightly longer traces due to the S Pin being on the other side of the device.
There is clearly no Source Resistor.
As a double check, I measured the resistance from V- to Source Pin and it reads 0.14r just exactly the same as the shorted probes reads.
i suggest that you contact Greg Ball and ask him yourself Greg is the best person to answer your concerns....
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I don't have a concern.i suggest that you contact Greg Ball and ask him yourself Greg is the best person to answer your concerns....
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I see contradictory information being posted.
I see a link that purports to clarify the situation.
The concern should be with those that are trying to clone the "for public" amplifier.
I don't need to clone it.
I have one and as a result I have access to all the IP that the designer wants to release to his customers.
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with gate thresholds of 2 to 4 volts compared to 0.6 volts for a silicon bjt's,
i wonder what a 0.22 ohm source resistor can do....what current is needed?
there is a reason source resistors are not used.....
the experts here can shed more light....
There is an initial turn-on surge when you power-up. In simulations (using Cordell models) this surge current is quite large. The capacitors on the CCS front end will not control this part of the turn-on because the CCS wakes up too slowly. A few people have posted into the SKA forum that they have used a soft-start module in their power supply to kill this turn-on thump. YMMV
As far as I can see the only reason why there isn't a source resistor on each FET is because the use of source resistors was an after-thought and Greg doesn't have enough space on his pcb to fit 4 power resistors and keep the neat traces. You need neat traces on this amp - it has at least two different frequency ranges it likes to oscillate if you get the pcb 'wrong'.
Yes, the 0.15 ohm resistors were added a few years ago and the OE boards were changed. Mine doesn't have them, but I believe Mike Gergen added some to his old-version boards, through some ingenuity with the traces underneath. My understanding is that it helps with the constant bias fluctuations experienced with the old layout, although I can report mine has been completely reliable and has been used daily for some years now.
Is it worthwhile to rise the value of these resistors?imho, the 0.15 ohm resistor in series with the rails is too small for normal operation, but big enough to assist in surge protection during startup....
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