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LM4780

siva prasad2
Prodigy 110 points

hi,

i have made an amplifier of 60W+60W using LM4780 with refference from the application ciruit from the data sheet.

i have tested the board with 34/0/-34 volts supply at 4ohms load, sound quality is good but less power comared to 20W amplifier TDA2030.

again i have tested the board with 12/0/-12 volts supply at 4ohms load, the sound quality is good but output power is same.

what is the problem with design ?

gain is 21, all connections are good.

can i any one tell me, did you have the same problem before and what is  the solution ?

 

  • 0
    TI__Expert 3840 points

    Hi Siva,

    Which circuit in the datasheet are you using? Is it a single-ended output design or a bridged-output design?

    When you say the output power is less than the TDA2030, how are you testing it and what brings you to this conclusion? ie. what do the sinewave waveforms look like and what are their peak-to-peak voltages? 

    Best Regards,

    JD

  • 0 in reply to John De Celles
    Prodigy 110 points

    Hi JD,

    Thank you for your responce and replay,

    i have made single ended only i.e 60W+60W,

    Actual I didn’t test the out power with any scope or multimeter because I have no availability of test equipment, I said that the power is less not by measuring by listening. Today I have found that TDA2030 amplifier sounds louder but it not clear I think lot of THD, but in case of LM4780 the sound quality is very good.

    One thing I couldn’t understand that LM4780 gives same sound when connected to 12/0/-12 and 35/0/-35.

    Regards

    Siva Prasad

  • 0 in reply to siva prasad2
    TI__Expert 3840 points

    Hi Siva,

    Are you sure that both amplifiers have the same exact circuit topology, components and values? This would be important to ensure when performing an AB comparison on sound quality. Any deviation in low-end frequency response, gain, component type, etc can and will affect sound level and quality.

    With respect to the LM4780 sound quality for different supply voltages, the two different values really wouldn't come into effect unless you were driving the amplifier hard and loud, in which case you would probably be driving the amplifier into clipping on the low voltage supply. Additionally, I would question the VA capability of the supply differences as you drive the amplifier harder on the higher supply voltage, you will need more current.

    Best Regards,

    JD