my 1st ever D-amp, WORKING!!!

[Pafi]

Don't forget about Qrr, and trr!

30-40 ns rise time and fall time is enough for an amp, you don't need faster, but 200-300 ns of trr is definitely too much.

IRF740: There is no N, but there is A, LC, and there is a variant made by ST, wich is the fastest.

I recommend FDP2572, but if you want some really fast, then buy IRF6665!

 

[Pafi]

I missed an important parameter: "Peak Diode Recovery voltage slope".

 

[RX5]

Hello PAfi,

nice info there.... ill go look again for those Qrr and trr....

IRF740: There is no N, but there is A, LC, and there is a variant made by ST, wich is the fastest.

had not know that until NOW...


PHP18NQ11T has some REAL NICE specs too... im dreaming

IRF6665.. digital audio MOSFET... waaaaahhhhh!!! how on earth do YOU find those kind of MOSFETs??

I usually download datasheet/s when I see an unknown part/#..


as of now, I would like to change the 2N2222A(part of the modulator) with BC546 - BC550 (these are switching types) and the "TURN-ON" mosfet driver 2907 with BC556 - BC560(also switching types).... the "TURN-OFF 2907, is quiet OK...


thanks,
Raff

 

[RX5]

Pafi,

since you have mentioned Qrr,trr :

IRF640N has faster td(on) td(off) BUT higher trr Qrr

IRF540N has slower td(on) td(off) BUT lower trr Qrr


so w/c do you think is better here??

should I stay below trr = 200ns ??

 

[Baldin]

I guess that the trr doesent matter if you are using a diode like ES2D across SD ... right

FDP2572 looks nice

IRF6665 really nice, but how do you mount these without a reflow oven

 

[RX5]

I guess that the trr doesent matter if you are using a diode like ES2D across SD ... right

Hello Baldin,

I didnt quiet get it... come again??? "where" is this diode??



duh!! i need to sleep.. its 4am here...

 

[Pafi]

A diode like this can conduct only 5...20 % of drain current. Maybe a shottky can do the job.

IRF6665 really nice, but how do you mount these without a reflow oven

Maybe via via.

 

[RX5]

hello guys,

check this out... list of MOSFETs.... you can add something and post back.. if you like....

does it lack something ... or missing ??


Regards,
Raff

 

[RX5]

I plan to experiment on using the IRFZ24N.... it has some really nice specs (correct me if im wrong)... only problem is its only a 55V device....

the question is CAN I SAFELY use it with a +/-30V (+/-42V unloaded)power supply??

if only the NICER mosfets were locally available....

 

[Pafi]

its only a 55V device.... CAN I SAFELY use it with a +/-30V (+/-42V unloaded)power supply??

No, you cannot use it at all! Think it over! When one FET is on, then the whole supply (2*42V=84V) is on the other FET!

 

[RX5]

No, you cannot use it at all! Think it over! When one FET is on, then the whole supply (2*42V=84V) is on the other FET!

oh.... ok?? I thought only HALF of the supply is going PAST 1 MOSFET.... but how come my IRF540N (100V) did NOT blow-up when I powered my diy UCD with +/-55VDC?



so I guess I COULD use the IRFZ24N with MAX supply of ONLY +/-15V (+/-21 unloaded) hehehe

talk about low power from the ucd....

well, I could live with that... +/-18 @ 4A power supply... might as well keep it in my room.... Im really INTO the specs with the IRFZ24N... might actually try it out sooner or later...

im more into sound Quality now... with the "faster" mosfets.....LESS with the power and MORE with quality sound reproduction..... im forced to.... if only ... whew


cheers,
Raff

 

[Pafi]

100V is guaranteed minimum, but actual breakdown voltage can be 5-20% higher.

 

[RX5]

But you DO agree that the IRFZ24N has nice specs right?? or maybe its just me dreaming

 

[Pafi]

It's not bad, but there are others with the same or better spec. Eg. BUK7575-55

 

[RX5]

ok.. i will see if those BUK are currently available...

 

[RX5]

no BUK.. too bad


anyway, changed some parts (current mirror and 'turn-ON' mosfet driver) to switching types.... changed also mt IRF540N to IRFZ24N && IRFZ48N.. still have to buy another 24N tommorow... and changed my power supply +/-48VDC to +/-24VDC(unloaded)....

guess what??

I had to RE-adjust deadtime.... so it means amp is oscillating at a diff frew now... mainly due to a -bit- improved MOSFET ..... but only a LOWER power suppy... anyways, its works!! and Im happy with it....

and an improved audio too...

 

[Pafi]

Do you have an oscilloscope? It would be interesting to see waveforms!

 

[RX5]

sorry I got none

I probably have to stick-n-play with a mono version and keep the other one stashed safely.. until I finally order or get some free samples from Fairchild... but is still months to come..


might be content with lower Vdss of mosfets BUT faster switching components... what a trade-off... lower supply BUT greater sounding amp vs. HIGHER supply (higher wattage output) but amp forced to -follow- slower switching parts...


UCD rocks!




cheers,
Raff

 

[RX5]

my UCD80 update yup!! 80, not 180... hahah


scenario:
downtown area... had to buy IRFZ24N.... 1st store, got only 2 of them,ran out of stock.... the other store had MANY but was only IRFZ24.. no "N"..... have to wait for another set of IRFZ24N's.... those are the ONLY locally avialable "FASTEST" switchers I could get... but its (Z24N) specs are pretty much close (or better) than PHP18NQ11T (my model mosfet).. only drawback is its Vdss = 55V... thats WHY I lowered supply from

+/-48VDC down to +/-24VDC.... at least THIS diy UCD sounds much better than using IRF540N switchers..

my 1st channel has identical IRFZ24N... the other channel has IRZ24N and IRFZ48N..



power supply : +/-18V (+/-24VDC unloaded) @ 3A

Dc offset with NO speakers attached :

-->>>with coupling caps:
Current source_ON = 5.6mV // source_OFF = -3V

--->>>DC coupled (coupling cap/s removed/shorted)
Current source_ON = 35mV // source_OFF = -650mV

DC coupled sounds much "better" i dont know the exact term....

AND, IRFZ24N mosfets sounds MUCH better than using IRF540N....

If I manage to get a hold of the higher Vdss//faster MOSFETS, then I would go back to using +/-48VDC


anyways, thats all for now....


last stock of IRFZ24N(here in tacloban) made by IR... part# is engraved...

 

[Tekko]

Why the AL foil on the legs ?

If its for esd, never had a prollem with that and i never put anything on the fets legs.