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About a simple class D amp

V

Vladimir Vassilevsky

Jan 1, 1970
0
MooseFET wrote:


Another idea:


in ---!!---/\/\--+------/\/\-----+---))))---!!--- Out
! !
! !\ HC14 !
+---! >O--------
! !/

With HC14, you have six gates anyway. I believe there used to be a
standard design of a reasonable class D amp using one 4069 and two FETs.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
 
M

MooseFET

Jan 1, 1970
0
With HC14, you have six gates anyway. I believe there used to be a
standard design of a reasonable class D amp using one 4069 and two FETs.

Many years back I saw one that used CD4049s. The whole circuit used
the 4049 as all of the gain and switching elements. Someone did it as
a joke in the first place.

Many years ago I made my own class D power amplifier. It sounded very
good. The whole thing was discrete. The sawtooth was very linear and
the comparators were fairly fast. This made the open loop linearity
fairly good. The feedback cleaned it up the rest of the way.
 
V

Vladimir Vassilevsky

Jan 1, 1970
0
MooseFET wrote:

Many years ago I made my own class D power amplifier. It sounded very
good. The whole thing was discrete. The sawtooth was very linear and
the comparators were fairly fast. This made the open loop linearity
fairly good. The feedback cleaned it up the rest of the way.

Class D amps is one of the things that I design as the business.

There is big problem with the open loop linearity of the class D: the
effective time of switching depends on the operating point. There is a
knee in the transfer curve between the continuos current and
discontinuous current conduction modes. Due to that effect, the
attainable open loop THD is at the order of 0.5...1%. The feedback of
the 1-st order has to be shallow, and the feedback of the higher order
distorts the saw. Higher clock rate is a cure for many sins, for the
cost of EMI and power. It takes a lot of optimization to get the quality
audio from the class D amp while maintaining the good power efficiency.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
 
J

Jasen Betts

Jan 1, 1970
0
Hi

I was, since few months, looking for an easy to build PWM inverter, and
without any PIC programing.

Looking again at the 555 PWM amp circuit, I have an ideas, by merging a
500 w sine inverter with the PWM section of the 555 PWM amp circuit it
made a PWM inverter.

Here is the final circuit.

http://img205.imageshack.us/img205/4066/invertersine500wccpwm.jpg

It should work... I think...

you'll need stronger gate-drive on the mosfets
also need a transformer that can handle the harmonics without overheating.
 
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