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    speaker operation problem in proteus

    Hello,
    I have designed an amplifier circuit that shows some result if I use 10k resistor as a load. But when I use a speaker no signal comes. What's the problem? All I have done in Proteus software. schematic is here Click image for larger version. 

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    •   Alt3rd March 2013, 08:29

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    Re: speaker operation problem in proteus

    1. TL082 cannot provide enough output current to drive a loudspeaker.
    2. You have a very high attenuation from the 10K resistor in series with the output. For example, if you have an 8 Ohm loudspeaker the volume is dropped 10,000:8 or by about 1250 times. With a 10K load it's only dropped to half.

    Brian.
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    •   Alt3rd March 2013, 10:44

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    Re: speaker operation problem in proteus

    it is because speaker has 8ohm
    and your load is 10k
    If you Believe everything you Read, Better Don't Read!



    •   Alt4th March 2013, 07:49

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    Re: speaker operation problem in proteus

    Quote Originally Posted by betwixt View Post
    1. TL082 cannot provide enough output current to drive a loudspeaker.
    2. You have a very high attenuation from the 10K resistor in series with the output. For example, if you have an 8 Ohm loudspeaker the volume is dropped 10,000:8 or by about 1250 times. With a 10K load it's only dropped to half.

    Brian.
    Which op-amp I should use to provide enough current.



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    Re: speaker operation problem in proteus

    None! You should use an audio power amplifier instead. Amplifiers like the TL082 are extremely good at amplifying voltages but are not designed to provide much output current. In fact they have an internal resistor in series with their output pin which limits the current they can deliver so it's impossible to get more than about 12mW (0.012W) from them in to an 8 Ohm load.

    If you use an IC the one you choose depends on how much power you want to produce, for small loudspeakers or headphones the LM386 is a good choice.

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    Re: speaker operation problem in proteus

    Quote Originally Posted by betwixt View Post
    None! You should use an audio power amplifier instead. Amplifiers like the TL082 are extremely good at amplifying voltages but are not designed to provide much output current. In fact they have an internal resistor in series with their output pin which limits the current they can deliver so it's impossible to get more than about 12mW (0.012W) from them in to an 8 Ohm load.

    If you use an IC the one you choose depends on how much power you want to produce, for small loudspeakers or headphones the LM386 is a good choice.

    Brian.
    If i use output to sample using Microcontroller, does the circuit work? Mentionable as TL082/TL072 is a good voltage amplifier.



    •   Alt4th March 2013, 12:14

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    Re: speaker operation problem in proteus

    Probably not but it depends on your supply voltage and what exactly you want to sample. Are you trying to sample the audio to record/analyze it or are you trying to find it's envelope amplitude?

    To find the envelope amplitude (like a VU meter) you must remove the DC voltage from the output of the TL082 and then recify and filter the remaining signal.

    To record/analyze (digitize the waveform) you must center the TL082 output voltage at the mid voltage of the ADC. Your circuit already does this with R3 & R4 but most ADC only accept input voltages between 0V and +5V so to have a mid rail of 2.5V you must also run the TL082 from a single 5V supply. My data sheet doesn't specify a lower operating voltage for a TL082 but the specifications go off the graphs at around 8V supply so you might be pushing your luck to get one working properly at such low voltage.


    Brian.
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    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.


    1 members found this post helpful.

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