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How do I simulate an audio amplifier in Multisim?

I'm required to search for audio power amplifier circuit and explain how it works in details so I need to know the detailed process of this circuit and understand how does it work? also I found this circuit from here SE

enter image description here

Fatima Aljneibi
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    Q1: Is this an assignment? Q2: What do you know about op-amps? Q3: Where did you get the circuit from. As shown it is incomplete and would not work properly. [Hint: The DC level of pin 2 MUST be defined] | Search the web for "zoebel network". – Russell McMahon Apr 27 '20 at 06:18
  • yes it is an assignment and I dont know much about op-amps and I got this circuit from this here stack exchange – Fatima Aljneibi Apr 27 '20 at 06:21
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    Please show the stack exchange page address || Q4: What is the actual assignment? ie if you must supply the circuit what are you actually required to do? – Russell McMahon Apr 27 '20 at 06:24
  • https://electronics.stackexchange.com/questions/76843/how-do-i-simulate-an-audio-amplifier-in-multisim/495960#495960 – Fatima Aljneibi Apr 27 '20 at 06:25
  • I'm required to search for audio power amplifier circuit and explain how it works – Fatima Aljneibi Apr 27 '20 at 06:27
  • @Fatima, welcome to EE.SE. All that information you have supplied should be added to your question, not hidden in the comments. Please [edit] your question to add it in. – Transistor Apr 27 '20 at 06:56
  • @Fatima, if you can search for **any** processor why would you select one you don't understand? – Oldfart Apr 27 '20 at 07:02
  • I need help in this please – Fatima Aljneibi Apr 27 '20 at 07:10
  • @FatimaAljneibi Unfortunately you have NOT chosen a "normal" circuit. The cct relates to a TDA2002 IC - [datasheet here](https://www.st.com/resource/en/datasheet/dm00028077.pdf) which has unusual connections. Pin 2 is allowed to have "AC coupling" via aa capacitor with this IC. This is NOT the case for every amplifier IC. I suggest that you look at the TDA2040 circuit [**here**](http://www.theorycircuit.com/25-watt-audio-power-amplifier-circuit/) which is very very similar BUT which connects the IC in a more standard manner. – Russell McMahon Apr 27 '20 at 09:36
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    You might be better off looking for a discrete transistor audio power amp, and explaining that. The details are visible there, instead of being hidden in an opaque triangular block. –  Apr 27 '20 at 10:25
  • I cant seem to find simple one since Q point and Amplifier classification are required most of the circuits are with op-amp – Fatima Aljneibi Apr 27 '20 at 10:35
  • You need to tell us ALL of your requirement "up front" so we can help you with the actual question. Note that while we do not "just answer" assignment type questions we are happy to help people understand such problems as long as they show effort in attempting to answer. || Q1: What is Qpoint (quiescent point - DC operating point or perhaps Class A AB B C ... biasing? or ...?) – Russell McMahon Apr 27 '20 at 11:04
  • I will post the assignment requirement in another question sir – Fatima Aljneibi Apr 27 '20 at 17:32

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This is just a simple Opamp .R2,R3 are sized for a closed loop gain of 101 .The output stage is more robust than normal opamps so it will drive a low impedance speaker .Biasing is internal so the audio is AC coupled with C1.C2.

Autistic
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  • Thank you so much – Fatima Aljneibi Apr 27 '20 at 07:26
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    You are correct re the internal biasing, but that risks being "hand wavium" for the OP. If they are asked to explain it they will be unable to do so. Note that pin 2 has NO DC coupling. The circuit will not work for a standard opamp. The TDA2002 which this applies to has a transistor input stage where pin 2 is effectively ground and pin 3 is single ended AC coupled input – Russell McMahon Apr 27 '20 at 09:51
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Unfortunately you have NOT chosen a "normal" circuit.
The chosen circuit relates to a TDA2002 IC - datasheet here which has unusual connections.
With this IC Pin 2 is allowed to have "AC coupling" via a capacitor due to the IC being "unusually constructed" internally.
This is NOT the case for every amplifier IC or for standard opamps - the diagram you are using would not work wity standard opamps or many other amplifier ICs.

I suggest that you look at the TDA2040 circuit here which is very very similar BUT which connects the IC in a more standard manner.

TDA2040 datasheet here
The diagram below is taken from fig 13 of the datasheet.

This diagram, from the above page, operates in a standard manner and is a MUCH better example for your purposes.

DO NOT just copy the following. Use it as a starting point for understanding. Ask questions if you need to.

R2 & R3 set the DC level of the amplifier's pin 1 input at about half supply voltage.
R5 ensures that Vout properly tracks the pin 1 DC level.
R5 and R4 set the AC gain.
R6 C6 is a Zobel network - Google knows. C3 blocks DC from the speaker.

enter image description here

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SIMPLE ALTERNATIVE:

OR the LM358 circuit from this SE EE question is very simple and may suit your need.

Note - this is a "preamplifier" in that it amplifies the microphone signal to a level suited to the main amplifier. It does however demonstrate the principles that you are required to explain, except for the power level.

Russell McMahon
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