constructing an audio power amplifier circuit

Thread Starter

sakuragurl

Joined Sep 27, 2008
14
Hey, i would like to ask how do you construct and audio power amplifier circuit using TDA2822M ?? can anyone show me a simple sketching of the circuit please?? Thanks!!
 

Skeebopstop

Joined Jan 9, 2009
358
I don't get why in the stereo implementation they don't use the L and R differential inputs as differential. Aren't audio signals just differential? So why connect the - terminal of the audio amp through a de-coupling cap to common ground, and not signal -?
 

Audioguru

Joined Dec 20, 2007
11,251
I don't get why in the stereo implementation they don't use the L and R differential inputs as differential. Aren't audio signals just differential? So why connect the - terminal of the audio amp through a de-coupling cap to common ground, and not signal -?
Most consumer audio sources are not differential. They have one signal wire and one ground wire which is the shield.

The (-) input of the TDA2822 is NOT the (-) terminal of the amplifier. It is a low impedance connection of its negative feedback. It would need to be buffered to have the same high input impedance of the (+) input. Then it would have a differential input.
 

Skeebopstop

Joined Jan 9, 2009
358
I'm just thinking of for example comms applications, where the signal gnd is routed inside with the signals but there is still a shielding separate to this to protect all of them from EMI etc.. RS232 or USB for example.

How is audio different? Low frequencies make it less susceptible to feeding EMI into your receiving end? After all, shields can only get rid of so much.. especially if connected to GND directly.
 

beenthere

Joined Apr 20, 2004
15,808
It may be that the shielding you refer to is to keep the signals from radiating out. Lots of sharp edges on those square waves.

USB is also a variant on LVDS, so not likely to pick up interference on low impedance twisted pair signal wires.
 

Thread Starter

sakuragurl

Joined Sep 27, 2008
14
hey, excuse me...what information can we include in the theory part of the circuit?? like how do we explain how the circuit works??
 

Thread Starter

sakuragurl

Joined Sep 27, 2008
14
hey, ...what information can we include in the theory part of the circuit?? like how do we explain how the circuit works?
 

bertus

Joined Apr 5, 2008
20,040
Hello,

On the page beenthere gave is also a link to the datasheet.
The datasheet will give you a lot of information.

Greetings,
Bertus
 

Audioguru

Joined Dec 20, 2007
11,251
hey, excuse me...what information can we include in the theory part of the circuit?? like how do we explain how the circuit works??
It is a simple stereo audio amplifier. Its schematic showing about 40 transistors is in its datasheet. It shows a darlington differential input, a voltage amplifier and a quasi-complementary output stage. It also has a bias circuit built-in.

The schematic in the datasheet for the TDA2822M is very fuzzy. It is much clearer in the datasheet for the TDA2822.
 

KL7AJ

Joined Nov 4, 2008
2,208
Most consumer audio sources are not differential. They have one signal wire and one ground wire which is the shield.

The (-) input of the TDA2822 is NOT the (-) terminal of the amplifier. It is a low impedance connection of its negative feedback. It would need to be buffered to have the same high input impedance of the (+) input. Then it would have a differential input.

One neat trick you CAN do with this, however, is to double your output power (in MONO mode) by driving the inputs and outputs differentially.

But yes...for 99% of all consumer audio equipment, everything is single ended.

eric
 

Thread Starter

sakuragurl

Joined Sep 27, 2008
14
oh yeah....i would like to understand about how do we know which capacitor values are to be used? and if different values of capacitors are used...how does it affect the circuit? from what i know, capacitors main function is to filter DC and to allow AC to pass through besides helping to amplify the output voltage...
 
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