CLASS D AMPLIFIER - reading material(prefer) and design help

[g.s.javed]

prefer amplifier

HI
I would like to design a class D amplifier. Could you help me by giving the reading materials/ literature to help me start off with the design and also design.

Any other suggestions on this topic are welcome.

Though old, I would like to implement the amplifier in CMOS .25u and also Bipolar 2u technologies.

This is what I know as of now:
Class D amplifier - is a non-linear amplifier.
- Has very high efficiencies.
- psrr = nearly 0dB
- Mostly used as an audio amplifier
- topologies are similar to PWM amplifier .

If there is anything incorrect, please (humbly request) correct .
this finally needs to be implemented on ans ASIC.
In that point of view, please pass on the material and knowledge.

Thank you in advance.

 

[throwaway18]

class d amp design

There are many possible topology's for switching amplifiers

Crown audio's patented system seems to work well, as I understand it they have two 50% duty cycle square wave signals and they phase shift one carrier, instead of trying to directly generate very narrow pulses during low volume parts of the audio.
It seems to work better than amplifiers using the old triangle-wave-generator and compator approach.

**broken link removed**

Here is a really interesting document from an amplifier manufacturer called hypex, I don't remember enough about control theory to understand all of it.

**broken link removed**

>Class D amplifier - is a non-linear amplifier.
The overall transfer characteristic should be reasonably linear, it's just the internal switching that is on or off instead of linear

>Has very high efficiencies

From what I have seen 85% is about the most people manage in reality.
Loudspeakers can be significantly reactive at some frequencys, they don't look just like a resistor. Some amplifers have much better efficiencys than others when driving partly reactive loads.

>psrr = nearly 0dB

Overall PSRR of the whole amplifier can be ok with good design.
I'v seen a design with awful PSRR (worse than 0dB) because all
the analog signals were referenced to a middle-voltage generated
from the supply using two resistors.

>Mostly used as an audio amplifier
yes, though magnatec claim they sell lots (with response to DC)
for motor drives in guided missiles.

If this is for a high power amplifier I expect you will be trying to drive
the gates of big FET's from your ASIC?

Overload and short circuit protection in big amplifiers can be tricky to get right.

 

[Kral]

prefer point 10

Try http://www.irf.com/technical-info/appnotes/an-1071.pdf. You will get lots of hits on Google by seaching For "Class D" Amplifier.
Regards,
Kral

 

[g.s.javed]

class d amplifier

Thank you.

@Kral
The document you mentioned does give a lot of information. I would like to know what would the typical specs of a class D amplifier be.
I have a start up problem :!:

 

[Prototyp_V1.0]

class a amp

Try http://www.irf.com/technical-info/appnotes/an-1071.pdf. You will get lots of hits on Google by seaching For "Class D" Amplifier.
Regards,
Kral

It looks that Fig 1 has an error. Shouldn't the feedback wire be mountetd on the other side of the inductor?

 

[Kral]

prefer point 10 amplifier

The following APP note gives some typical values for efficiency and distortion for a high power Class D amplifier.
http://www.irf.com/technical-info/appnotes/an-1070.pdf
Another consideration is EMI emisison, which is considerably higher for a class D amp than with a class A, AB or B. This issue is covered at **broken link removed**.
Regards,
Kral

Added after 3 minutes:

I believe Prototyp_V1.0 is correct regarding the feedback connection

 

[g.s.javed]

amplificatore classe d magna tec

can u simplify the explanation please???
I couldn't make out the difference , why the feedback point should be shifted?

 

[Prototyp_V1.0]

switching amplifiers non class d

can u simplify the explanation please???
I couldn't make out the difference , why the feedback point should be shifted?

Because as it's drawn now, output voltage is not to be in the feedback wire, but rather the pmw pulses.

 

[nilamrmehta]

i want to make power amplifier in class E in push pull configuration using any IRF MOSFET And output of 1000W at low cost.
if you have any circuit or any informatio for MOSFET then give me reply.