Thread Starter

joan0113

Joined Jan 13, 2022
2
Hi, guys!
The LM358 OPA and LM393 Comparartor are two common jellybean components that are characterized by their ease of use and availability. Outwardly, the LM358 and LM393 are very similar–they come in the same package and with the same pinout, but are they interchangeable?
I would appreciate it if you could help me out.
Looking forward to your reply!
Best regards!
Joan
 
Last edited by a moderator:

DickCappels

Joined Aug 21, 2008
8,671
No.

The LM393 has no frequency compensation and no pull-up on its output.

I once saw an application note in which a comparator was used as an opamp but it external frequecy compensation by making the pull-up output circuit very, very slow.

Edit: Corrected part number per Ian0 in post #3.
 
Last edited:

Ian0

Joined Aug 7, 2020
4,821
No.

The LM358 has no frequency compensation and no pull-up on its output.

I once saw an application note in which a comparator was used as an opamp but it external frequecy compensation by making the pull-up output circuit very, very slow.
You mean the LM393?
 

Ian0

Joined Aug 7, 2020
4,821
Hi, guys!
The LM358 OPA and LM339 Comparartor are two common jellybean components that are characterized by their ease of use and availability. Outwardly, the LM358 and LM393 are very similar–they come in the same package and with the same pinout, but are they interchangeable?
I would appreciate it if you could help me out.
Looking forward to your reply!
Best regards!
Joan
No, they’re not - one is an amplifier (LM358) and one is a comparator (LM393).
http://encon.fke.utm.my/nikd/latest/sloa067.pdf
There are some applications where you can use an op-amp as a comparator, and the LM358 is one of a small number of op-amps which will function as a comparator albeit with a very slow output.
If the output drives logic gates, some of them will not like the slow rise time, and only a proper comparator will suffice.
It is very unlikely you could use a comparator as an op-amp, in most cases it will oscillate.
 

DickCappels

Joined Aug 21, 2008
8,671
You mean the LM393?
You are right! Thank you for catching that. The error has been corrected.

I would like to add that the pins are arranged so that the inverting input pin is between the output pin and the non-inverting input on both devices because this reduces chances for oscillations and ringing. Putting the power supply connections in those corners is very common. The pin-outs are similar for those reasons.
 

Ian0

Joined Aug 7, 2020
4,821
Would I be going to far to say that all dual op-amps and all dual comparators have the same pin out as the LM358/LM393?
But don’t get carried away as the quads (LM324/LM339) have different pin outs.
 
Top