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I want to use RC4558 as a low pass filter for a subwoofer. But, because of the lockdown situation, I am unable to get one. I only have LM741 in my package.

How can an LM741 IC replace a RC4558? I read that RC4558 is a dual version of LM741 op-amp.

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  • \$\begingroup\$ You open the datasheets and compare them, if you can replace one RC4558 with two LM741. If there are differences needed, like changing some feedback resistances, you have to take that into account too. \$\endgroup\$ – Justme Jul 3 at 18:12
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    \$\begingroup\$ They are both about 40 years behind the times. \$\endgroup\$ – Brian Drummond Jul 3 at 18:12
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    \$\begingroup\$ Consider using the TL0xx series or the OPAxx series. Profoundly better performance. \$\endgroup\$ – user105652 Jul 3 at 18:25
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    \$\begingroup\$ It's for you to read the datasheet, I'm afraid. \$\endgroup\$ – TonyM Jul 3 at 18:38
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    \$\begingroup\$ Vishal, why are you on a spiritual journey to find the worst ICs in existence? Love yourself a bit, don't use such opamps. \$\endgroup\$ – Marcus Müller Jul 4 at 7:52
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From the RC4558 datasheet:

The RC4558 device is a dual general-purpose operational amplifier, with each half electrically similar to the μA741, except that offset null capability is not provided.

If your circuit is based on the RC4558, then it won't need the null adjust pins of the 741.

The RC4558 and the uA741 are both 8 pin chips, but the pin outs are different.

From the uA741 datasheet

enter image description here

From the RC4558 datasheet:

enter image description here

The pins don't match. Vcc- and IN+ and IN- match, but nothing else does.

You'll have two use two uA741 chips for each RC4558 you need to replace.

You'll have to modify the the schematic and layout to connect to the proper pins.

Connect by function.

  • 1In-, 1In+, and 1Out map to In-, In+, and Out on one uA741.
  • 2In-, 2In+, and 2Out map to In-, In+, and Out on the second uA741.
  • Vcc+ and Vcc- connect to both uA741 chips as usual.

This is why you use schematic diagrams rather than wiring diagrams.

The schematic shows the function of each pin, so rearranging to fit a different part is relatively straight forward.

The datasheet says the two ICs are functionally the same, so all you have to do is rewire things a bit.

If all you have is a wiring diagram, then you have no idea what goes where - so you have to start by drawing a schematic from the wiring diagram.


Q: What op amp is worse than the uA741?

A: The RC4558. It is twice as bad as the 741 because it is two grotty old 741s in one package.

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  • \$\begingroup\$ I got my answer, Thankyou. \$\endgroup\$ – Vishal Jul 3 at 19:22

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