Pepping up a Silicon Chip SC480 audio amplifier

Don't forget the nice beefy driver stage to charge and discharge that gate capacitance.

Graham

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yeah, my computer guys have suggested I try similar things, but always with the "not for the faint-hearted" caveat. My preference, however, is to buy a thing in a box, unpack it, plug it in and turn it on, then sit back with a beer.

but VFF is a lot better than watching ads in real time, so Im happy enough with that. I try hard to *only* watch time-delayed telly.

Cheers Terry

In the '90s I did a design for a low-power 2MHz diagonal half-bridge SMPS. INitially I used FETs, but when I looked at the H-field emanating from the gate traces (which were constrained to be on one layer, and long), I changed the switching devices to bipolars - for the same speed I required much less peak driver current. Sure, I had to cough up some continuous driver current, but that was a lot less than the peak.

I have a SMPS Im finishing off now that sucks 1W@12V, just to drive the gates of 6 hefty FETs - so much that I actually dropped Fsw to keep it under control. Once this design is in production I will design a resonant gate driver, and see how low I can reduce the gate losses.

oh yeah Graham, I cant see ABSE, so if you could email me those Toshiba datasheets it would be appreciated.

Cheers Terry

On Sat, 23 Aug 2008 11:03:39 +1200, Terry Given put finger to keyboard and composed:

- Franc Zabkar

--
Please remove one \'i\' from my address when replying by email.

ta. If I wasnt so dim, I could have typed them into google. duh.

Cheers Terry

** Not at all necessary for either wide small signal bandwidth ( as wanted by the OP) or where the load Z is fairly high - as is also the case with the OP's stated needs.

Mosfet gate drive is requirements are VERY modest when the output power level is lowish.

In any case, even with high power operation and parallel groups of lateral mosfets, the standard drive circuit is nothing more than a pair of TO92 plastic pack transistors like the MPSA42 and MPSA92 and gives slew rates of about +/- 50 volts per uS or 100kHz at full power.

..... Phil

"Eeysore"

** Shame how Ft is a strong function of Vce and Ic.

Ft drops like a stone below 0.5 amps and above 5 amps for those devices - and nearly all other power BJTs are much worse.

..... Phil