Nothing In Particular

[Nick]

Typo, should have been TO

http://www.mouser.co.uk/Search/ProductD ... TK110N20L2

[ed]

Typo, should have been TO

http://www.mouser.co.uk/Search/ProductD ... TK110N20L2

Phew!! thank the gods, I was beginning to feel a bit paranoid thinking the world was moving on without me.

diet: just had a quick look, isn't thermal stability a bit trixy? perhaps I need a better read.

[pre65]

Typo, should have been TO

http://www.mouser.co.uk/Search/ProductD ... TK110N20L2

Phew!! thank the gods, I was beginning to feel a bit paranoid thinking the world was moving on without me.

I was also a bit confused.

Must get round to making the 50W single ended mosfet amps more user friendly.

[Nick]

diet: just had a quick look, isn't thermal stability a bit trixy? perhaps I need a better read.

Well, may be fatal last words, but no, they seem fine, you do need to compensate for temperature, but as long as you do that they seem nice and stable. The amp does have a over temp panic stop (80C) , but I have only ever reached it by pointing a hot air gun at the sensor.

[Dave the bass]

Any chance you might send it to me when you've finished?

I'd like to Ed but its not mine to give away. It forms part of the Reference Library here in Cornwall.

I've just turned the (heavy and wipe clean surface) page and just read...
"Noisy Puppy wants Kitten to wake up and play.
'Purr,' goes Kitten, softly".

I don't think I can cope with the emotional intensity demanded by this book.

[ed]

diet: just had a quick look, isn't thermal stability a bit trixy? perhaps I need a better read.

Well, may be fatal last words, but no, they seem fine, you do need to compensate for temperature, but as long as you do that they seem nice and stable. The amp does have a over temp panic stop (80C) , but I have only ever reached it by pointing a hot air gun at the sensor.

was there something in particular that grabbed your attention for this....
I've just looked in a bit more detail and the capacitance looks worse than the irfp240s I have in the box.

[Nick]

The capacitance is horrible.

The logic went:

1. Build 300b set, listen to it and think how wonderful it is, then play some vinyl and think where has the wonder gone?

2. Decide all the LF information in the vinyl is causing the SET to saturate the transformer

3. Decide that I like bass and rock music, and SET won't do it with the loudspeakers I can afford

4. Wonder why some solid state amps sound better than others, and wonder if all those parallel output devices do any harm

5. Look at what I can do to run a single N and single P output stage

6. Find the IXYS mosfets that have N and P, and have linear SOA on the chart, and have a single die construction unlike other large mosfets that are internally paralleled

7. Build prototype using mosfet driver chip and mosfet buffer to drive output mosfets, spend some time getting it stable (took to Owston, went down well)

8. Build second prototype using own designed driver stage and bipolar buffer, seems good, spend a lot of time getting it stable and working as I wanted

9. Build into casework

10. Build some more

11. Make 100w version

[Nick]

There was also a lot of staring at square waves with a 500Mhz scope, thrashing dummy loads, peering at the corner of clipped sine waves. running spice sims and buying a second had R&S UPL in that process as well.

I just could not keep those devices under control with a conventional driver stage, a inverted driver like the f5 may have worked, but that would not be able to driver the nF's of gate capacitance, so I stole ideas from the switching driver guys, and ended up pushing watts of power into the grid.

In someways not a problem unlike A2 drivers.

[ed]

The capacitance is horrible.



6. Find the IXYS mosfets that have N and P, and have linear SOA on the chart, and have a single die construction unlike other large mosfets that are internally paralleled

7. Build prototype using mosfet driver chip and mosfet buffer to drive output mosfets, spend some time getting it stable (took to Owston, went down well)

even more intrigued.....you're gonna really hate me now......

whats the benefit of single die construction, I know I could probably google it but....

and why the passion for N and P, I'm still wading through pseudo complimentary, but it looks safer in some respects, and closer to where we came from......that might be a very naive question and if so please ignore it for the time being

diet: posts overlapped.....I see I'm in deeper water than I at first thought

[Dave the bass]

"it all sounds too easy...."

Not!

2 Wayne's World reference's in 1 reply , a bonus point fo sho!

[Nick]

All IMHO of course.

Without single die construction there is nothing to be gained from using a single output device, in fact more is lost as you can't use a source resister under each one to stop current hogging. It doesnt matter if you are switching them all on or all off, but if you are in the middle it does. Thats why I was interested in IXYS having these devices that were advertised for linear use, and were somewhat rugged.

The dislike of N and P is the same reason I dislike futterman like OTL circuits, the source resistance of a cathode and a anode will never be close, likewise a source and drain will never be close, yes you can wrap it all in feedback and hope its all ok, but I prefer symmetry if possible. With valves you have no choice, with silicon you do. IXYS don't advertise the two as complementary, but they are close enough.

[ed]

"it all sounds too easy...."

Not!

2 Wayne's World reference's in 1 reply , a bonus point fo sho!

shut up you!, how can I concentrate?, an I need to concentrate, this tuff's trixy

[jack]

This is really interesting. I used a lot of gate drivers in my Tesla Coil days, but they were all two-state, on or off, never linear. High Qg in low RDSon high voltage FETs were always a bitch to drive, so I tended to use either Maxim devices or the ubiquitous UCC36321/2 chips. For HV isolation we use GDTs which also wouldn't help linearity... but then again, linearity wasn't the objective....

However, using a high current output rail to rail opamp like the LM8261 might work well, or an equivalent bipolar driver...

I'm sure a single or double stage discrete driver could do that.

More things to Investigate...

EDIT: The LM8261 is the right idea but way too low drive... but using it to drive a two stage PP buffer and taking the local FB from the buffer output/gate would be both linear and pretty stable...

[Dave the bass]

"it all sounds too easy...."

Not!

2 Wayne's World reference's in 1 reply , a bonus point fo sho!

shut up you!, how can I concentrate?, an I need to concentrate, this tuff's trixy

Heheheheh. FWIW, I'm concentratin' too even though we're on Hols, PSU book down the PUb with JTS.
We're not very good at conversation....

[pre65]

I went out in the new car last night to test the lights.

The dipped beam is HID, and seemed a bit low. On checking where the adjuster is it seems it's automatic, with sensors front and back.

Checking on the interweb it seems the sensors have a connecting rod to the suspension arm, and are prone to siezing up and then snapping.

I took the RH wheel off to check the rear one, it had not broken, but upon removing it both ball joints were siezed. The rubber boots were split, but as a temporary fix I squirted WD40 in and wiggled them about, so now they wobble and have been refitted.

I'll check tonight and see if it's made a difference to the dipped beam height.

As these link rods don't seem to be a Honda spare part, I've got a couple of M6 ball joints coming (Ebay) and will join them with some M6 rod I have in stock. That way I can fine tune the adjustment to take into account suspension droop.

http://www.ebay.co.uk/itm/M6-x-1mm-Male ... 1438.l2649



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