Does this D Amp really work?

The patent they cite (03/090343) does appear to be for a self-oscillating switching-amp circuit.

It looks to me as if the Q1/Q2 pair is (in effect) comparing the input signal with an attenuated version of the output (feedback from output J10, via the R11/R12 ladder) and the results of this comparison modules the duty cycle of a drive signal coming out of Q5-Q8.

--
Dave Platt                                    AE6EO
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"Harry Dellamano"

** The technology is right there in front of your eyes - just look how the main NFB loop take off comes AFTER an L-C filter at the output. Recipe for HF oscillations - no ?

Here is the web site of the guy ( Bruno Putzeys) who invented that arrangement - while employed by Philips.

Apparently, he has to pay them royalties use it himself.

...... Phil

While the input comparator and level shifting techniques are not discussed, the self-oscillating topology and it's variants are covered pretty well by Bruno Putzeys in his AES conference paper from '05.

"Simple Self-Oscillating Class D Amplifier with Full Output Filter Control" Bruno Putzeys, Philips Applied Technologies, BE3001 Leuven, Belgium, AES 118th Convention 2005 May 28.31 Barcelona, Spain

The self oscillating PWMPA has been around for some time.

Please note the precautions in the UM10155 article. It is sometimes not enough just to 'go'.

RL

If your html portal to usenet can't handle it, cut and paste the address into the address window and press enter on your keyboard. The target is a pdf file, so you need a reader for this format.

Alternately, right click and 'save link target as'.... RL

Server not found Firefox can't find the server at

Nice, it is simple, therefore elegant! With a name like Putzey he must have a lot of time on his hands. Thanks Phil, you are always so nice and helpful. Cheers, Harry

Truely, it was not new. I remember an Article in the Magazine "Elektor" from about 1978 where a tiny self-oscillating PWMPA was described, with PCB available. Consists of, when i remember right, one LM311 and a few transistors, AFAIK no MOSFETs as PA. Sony had a PWMPA in the late seventies on the marked, also.

Jorgen