# Full-digital audio amplifier

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#### jetmarc

##### Member level 3
audio amplifier pure digital

Hi. I am looking for example designs of full-digital audio amplifiers. I want to use a 250mW speaker with minimum external parts, especially without DAC. There are about 2k FPGA gates available to be dedicated to filtering and PWM. The source quality is mono 8khz 8bit.

Any suggestions?

Marc

#### Burger King

##### Newbie level 6
I don't know if this could help you. I've found a Xilinx appnote on the implementation of sigma delta converters in FPGA (as far as I know it's the only way to avoid adding an external DAC).

#### micijanus

##### Junior Member level 1
https://www.apogeeddx.com is the place to go,
And i would like to see the results of your efforts!
DDX2100 ic (i am looking for spice model)
also look at SA07 ic (spice available)

#### jetmarc

##### Member level 3
Thanks to both of you for the links. I have ordered samples of the DDX chip.

In fact I have a FPGA available in my circuit but I am a bit worried about the logic area necessary to filter the data. Did any of you actually implement such an amplifier in VHDL? I don't want to dedicate more than 2k gates to the audio (including DMA to fetch data from SRAM).

jetmarc

#### micijanus

##### Junior Member level 1
Also look at the SA07 @ https://www.apexmicrotech.com/products/index.html
The more expensive 97$500KHz SA07 (DDX2100 4$)can take both analog & digital signals directly to the chip - no controller. They give good developement tools. And no values on their poposed PCB - and that is where i need help. The only point that i like more on the DDX is the Damped Ternary Advantage over Binary. But i do not know how to put a spice model together for DDX
THNKS

Uploaded file: SA07 Hi Fidelity AUDIO Amplifier.pdf

#### andy2000a

what is digital audio Amp ?? look like class-D amplifier
class A --> good amp but efficiency =25%
class B --> have distrtion on signal =0
class AB --> bias on A<-> B use small bias
class C --> someone said Switch like Amp for RF
class D --> PWM amplifier ??? PWM is digital signal and use bridge + Low pass , it is digital audio Amp
, many toy chips use PWM driver speaker . but quality is poor

#### ynhe

##### Full Member level 3
Hi
It is impossible to simulate pure digital amp using SPICE.
The pure digital amp like apogee include Interpolation,Noise Shaping etc.
How to simulate using spice?
You may simulate using MATLAB.

The pure digital amp is not class D amp.

ynhe

#### andy2000a

I know what you said ..
digital amp == AC07 codec ssytem
it is pure digital and AC97 use delta-sigma D/A

deltaSigma A/D --> Nation semi or AnalogDevice have many paper
deltaSigma -> use C or matlab or hspice behavior simulation
but modulator is switch Comparator , it can simulation by spice , you can find many paper about it , but we usually matleb simulation system , hspice only simulation circuit

delta sigma D/A --> use digital filter --> codec analog chip
codec is Low pass filter

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