Today I received a signal generator and since the puck Mofo was playing in the system I used one channel as DUT.
First I ran some square waves then some sines.
With sines it does 2hz-1.6Mhz at -3db rolloff at both ends and is close to flat from 10hz-160khz.
Measured with 8ohms load.
First I ran some square waves then some sines.
With sines it does 2hz-1.6Mhz at -3db rolloff at both ends and is close to flat from 10hz-160khz.
Measured with 8ohms load.
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A 20v 5w part should do it. Maybe something like this (1N5357). I added a 1000uF cap to the DC input of the amp and it also prevents the sudden collapse of the coil well enough to protect the output mosfet.
I'm thinking of building a MoFo, it looks very interesting but I'm wondering about a few things.
How is thermal stability/bias drift?
Could a 'auto bias' circuit be a good idea? like:
Also M1 is dissipating a lot of constant heat (50w) would a CPU cooler be a good to cool this beast?
I have 24V 6A power bricks already, and am looking to making this (at least the prototype) nice and cheap.
Would a Hammond 159ZC at 60mH, 2A, 700mOhm (Digikey 159ZC) or a
Signal Transformer CH-4 at 70mH, 4A, 600mOhm (Digikey CH-4) be a good fit?
How much standing current could I take this up-to?
How is thermal stability/bias drift?
Could a 'auto bias' circuit be a good idea? like:
Also M1 is dissipating a lot of constant heat (50w) would a CPU cooler be a good to cool this beast?
I have 24V 6A power bricks already, and am looking to making this (at least the prototype) nice and cheap.
Would a Hammond 159ZC at 60mH, 2A, 700mOhm (Digikey 159ZC) or a
Signal Transformer CH-4 at 70mH, 4A, 600mOhm (Digikey CH-4) be a good fit?
How much standing current could I take this up-to?
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I built a MoFo like the original cct sans the zeners that idles at 2A.
The bias is very stable, does not fluctuate at all.
The beauty of Mr. MR's cct s it allows you to vary the bias if you want depending on your hardware requirements - sinks, choke, etc.
You will not have that flexibility with your idea.
Also I think IRFP240 is not that great in that position. Try something with more Gm, like 140, 150, 250. You can also try a puck, that will dissipate a lot of heat.
The bias is very stable, does not fluctuate at all.
The beauty of Mr. MR's cct s it allows you to vary the bias if you want depending on your hardware requirements - sinks, choke, etc.
You will not have that flexibility with your idea.
Also I think IRFP240 is not that great in that position. Try something with more Gm, like 140, 150, 250. You can also try a puck, that will dissipate a lot of heat.
Well if the bias is stable then better just to stick with a pot. I'm wondering would a capacitor between the wiper of the pot (P1) and ground be better to reduce power supply noise?
I have IRFP140's but I'd be concerned with the longevity of such a single TO-247 device.
By puck I presume its something like:
An IXYS IXFN73N30 is less than £10.
Looking way back at post #507 @Ralph G seems to have had good look with a IXFK44N50 and the Hammond 159ZC choke.
So either a puck style or 2x IRFP140's.. hmmmmm 🤔
I have IRFP140's but I'd be concerned with the longevity of such a single TO-247 device.
By puck I presume its something like:
An IXYS IXFN73N30 is less than £10.
Looking way back at post #507 @Ralph G seems to have had good look with a IXFK44N50 and the Hammond 159ZC choke.
So either a puck style or 2x IRFP140's.. hmmmmm 🤔
I use irfp150 in my MoFo at 2A.
Attached to a massive heatsink.
I also drop the PSU voltage to 22V through a CapMx, then couple more volts across the choke (MOT).
So 20V across the fet@2A is 40W.
The get seems not to mind it, has been running like that for 4-5 years now.
I wouldn't parallel 2 gets as then you'll need careful matching and source resistors. Kind of goes against the beauty of simplicity.
But it's up to you to experiment.
Attached to a massive heatsink.
I also drop the PSU voltage to 22V through a CapMx, then couple more volts across the choke (MOT).
So 20V across the fet@2A is 40W.
The get seems not to mind it, has been running like that for 4-5 years now.
I wouldn't parallel 2 gets as then you'll need careful matching and source resistors. Kind of goes against the beauty of simplicity.
But it's up to you to experiment.
