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What is the Difference Between the Normal Opamp LM741 and the Audio Power amplifier LM386..
I mean in both the circuit we use the concept of voltage compensation, then how come LM386 is called power amplification also,
What is the difference between Operational Amplifier and Power Amplifier though in both the circuit we are using external supply to drive the circuit?
Can a operational amplifier be power amplifier?
I am currently using LM386 with a microphone to amplify audio signals,
Can I replace the Microphone with Ultrasonic transducer and the amplifier still work?

Thanks,Regards

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    \$\begingroup\$ No evidence of any research whatsoever - question should be closed. \$\endgroup\$
    – Leon Heller
    Commented Apr 13, 2015 at 18:26

1 Answer 1

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Cars and big rigs have a lot in common but one's a car and the other's a truck. Here's a cut/paste from another forum (elec-tech-online):

if i were to design a discrete op amp, it would be very similar to a power amp design, except for the output stage, which would be just two small transistors for the op amp, but as many as 3 pairs of successively larger transistors (usually complementary pairs in a darlington configuration) for the power amp, because the power amp needs to source a lot of current to low impedance loads, while the op amp is usually used as a voltage amp .

And a summary of differences:

The 741 has inputs that must be close to half the DC supply voltage. The LM386 has inputs that work at its negative supply voltage that is usually 0V (ground).

The 741 has a max output current of about 20mA so it can drive a load of 2000 ohms. The LM386 has a max output current of about 810mA so it can drive an 8 ohm speaker.

The 741 needs negative feedback resistors added. The LM386 has built-in negative feedback resistors.

The 741 has trouble above 9kHz. The LM386 works well to 300kHz.

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  • \$\begingroup\$ What is meant by The 741 has a max output current of about 20mA so it can drive a load of 2000 ohms. and LM386 has a max output current of about 810mA so it can drive an 8 ohm speaker? \$\endgroup\$
    – sherrellbc
    Commented Apr 13, 2015 at 17:43
  • \$\begingroup\$ @carveone yes opamp uses Push-Pull Circuit at the Opamp Output....but magnifying the the current using Darlington pair in the power amplifier the current has to be issued from the supply itself right? \$\endgroup\$
    – AminoAcid
    Commented Apr 13, 2015 at 17:45
  • \$\begingroup\$ @sherrellbc: Imagine taking the output at, say, 5V and putting a resistor to ground. If the resistor was 8 ohms, 5V/8ohms = 625mA would flow. A 741 cannot drive this amount. To Original Poster - Yes, the current is issued from the supply but that's always the case :-) For a 741, the output stage is not designed for that much current, it'll just melt! \$\endgroup\$
    – carveone
    Commented Apr 14, 2015 at 10:35
  • \$\begingroup\$ @carveone thanks for the answer,My doubts are now clear,by the way they closed the question lol!!,this question cannot be answered by one not in profession as have to know the understanding of various schematic of the ICs, Thanks.Hail to Life!!! \$\endgroup\$
    – AminoAcid
    Commented Apr 14, 2015 at 16:49

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