Interesting schematic

[spare_parts]

Check out this little circuit! Any comments would be helpful as i intend to try this one out soon. It should be about 60w into 8ohms, and runs at 50khz. Notice the lack of output inductors?!? Should one be included even though the designer did not? There is a 'pulse shaping network' that looks like a zobel or snubber there, but...

[fernando_g]

1) I would choose a faster slewing opamp than the TL074.
2) Yes, an output filter will be necessary, if you plan to run your speaker wire more than a few inches (to prevent EMI)
3) Since +/-51 volts is way too high for a common linear regulator dual (LM317, LM337) without some pre-regulation, at the very least buffer the zeners with an emitter follower.
4) Much has been written about half-bridge topologies pumping the power supply. Don't know how serious this issue could be, but something you must be aware of.

[fredos]

I know this circuit...Old radio plan magazine..This amplifier was design for sub and run from floating 51V supply, not +/-51V...

[spare_parts]

I intend to use this for a small sub, and will mount the amp very close to the speaker, possibly allowing operation without an inductor. I may include an inductor, anyway, in the form of a 6db lowpass crossover at about 150hz. The power supply is labelled funny; it is really 51v total, +/-25.5v. Can an amp like this be bridged across the load (high enough impedance, of course) or would it be unstable in that configuration? I planned on just feeding an inverted signal to one channel. The circuit, BTW is from popular electronics magazine years ago, but I found it in a compilation of circuits in book form.

[spare_parts]

I have been working on a PCB and will post it soon if there is any interest.

[latala]

I must admit that I have been looking for something like this for ages I am very interested in all your efforts re this amp
regards Trev

[lumanauw]

For one half bridge, how can we adjust dead time? Put something around Q1-Q3?

[fredos]

Change front op amp for LM319 fast comparator, add PNP-NPN buffer on each FET and add low pass filter and it will work decently...I start from this idea to design my D-Amp 1200....Do research on forum, you will find schematics.

Fredos

[lumanauw]

Hi, Fredos,

I'm looking for adjustable deadtime, but with comparator front end. UCD is adjustable, but it is discrete. I wanted to use fast comparator.

From my experiment, this one has too little dead-time, making cross-conduction when the mosfets are hot. There are phases where both mosfets conduct. I can only change a the supply for the totem pole (+/-10V) to adjust a little, but that's it.

[lumanauw]

This one has too large dead time. Is there any adjustable dead time driver, where the comparator is only 1? Phase_Accurate's schematic is adjustable, but it use 2 comparator.