Why there is a bump in virtual ground point at lower feedback resistances in OpAmps?

Thread Starter

rockgro

Joined Sep 7, 2021
13
I was watching this great OpAmp video by EEVblog and there I was not able to figure out the reason for the bump in the virtual ground point with lower resistances.
link-
@48:31
Pls, help me with this!!
 

MrSalts

Joined Apr 2, 2020
1,762
Yep, the LM358 suffers from crossover distortions. Just wait for @Audioguru to show up and rail about this chip - he'll tell you it is not the best choice (it's a horrible choice) for audio of even reasonable quality.
 

Ian0

Joined Aug 7, 2020
5,138
Yep, the LM358 suffers from crossover distortions. Just wait for @Audioguru to show up and rail about this chip - he'll tell you it is not the best choice (it's a horrible choice) for audio of even reasonable quality.
I'll do it for him - it's a dreadful device. Never use it for audio. There are so many better op-amps for audio.
 

DickCappels

Joined Aug 21, 2008
8,710
But are there cheaper ones?

You can reduce the crossover distortion if not eliminate it by connecting a resistor from the output of the LM324/LM358 to its negative power supply terminal. This worked very well for me when buffering a low distortion 1 kHz sine wave. Driving a capacitive load might require a lower resistor value, or a better opamp.


1651386770524.png
 

Audioguru again

Joined Oct 21, 2019
4,685
The LM358 dual and LM324 quad opamps are the only opamps I have seen that produce crossover distortion that is huge at low output levels and high gain. also they are noisy and have a poor slew rate that restricts frequencies above 2kHz at high levels.

I used Motorola MC3317x single, dual and quad opamps instead for very low current single supply opamps that produce no crossover distortion and I have never added a resistor to the output of an LM358 to make it "a heater" without crossover distortion.
 

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KeithWalker

Joined Jul 10, 2017
2,354
The 4558 is a good replacement for the LM358. It has the same pin-out. It has low noise level, no crossover distortion.and 3MHz bandwidth.
 
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