op-amp

beenthere

Joined Apr 20, 2004
15,808
The pin-outs are clearly not the same. The LM741 is a single op amp, the LF358 is a dual.

Or are you asking something else?
 

Thread Starter

CircuitSurfer

Joined Sep 19, 2009
21
I haven't noticed that they are different. Thanks for pointing it out.
Can you tell me if pins 1,2,3,4 and 8 of LM358 correspond to pins 1,2,3,4 and 8 on LM741.
 

Wendy

Joined Mar 24, 2008
21,840
As a general rule of thumb, single op amps follow the same layouts, dual op amps follow the same layouts, and quads follow the same layouts. You can not mix a single with a dual or quad, and so on.

The LM339, a quad comparitor, has a totally different layout from quad op amps.
 

Thread Starter

CircuitSurfer

Joined Sep 19, 2009
21
I realize now that they are different. However my project only calls to use 5 out the 8 pins on the LM358 in effect I think it uses only one of the op-amp circuits. Since LM741 is a single op-amp I want to use that. Having said that what would be the substitute pins 4 and 8 of LM358 on LM741. Or their amplificatoin properties are completely different?
 

Tahmid

Joined Jul 2, 2008
344
Hi,
For LM358:
pin1 = out1
pin2 = -in1
pin3 = +in1
pin4 = gnd
pin5 = +in2
pin6 = -in2
pin7 = out2
pin8 = vcc

For 741:
pin1 = not required
pin2 = -in
pin3 = +in
pin4 = gnd
pin5 = not required
pin6 = out
pin7 = vcc
pin8 = not required

Pin4 of 741 and LM358 are the same. Pin8 of LM358 has the same function as pin7 of 741. The rest can be observed from the comparison I have mentioned above.
 

Audioguru

Joined Dec 20, 2007
11,251
The opamps are different and might not work if a 741 opamp is used instead of the LM358:
1) The LM358 works with a supply voltage as low as 3V. The 741 needs 10V or more.
2) The LM358 works when the input voltages are as low as the negative supply voltage. The 741 does not work unless its input voltages are higher than 3V above the negative supply voltage.
3) The output of an LM358 can go down as low as the negative supply voltage. The output of a 741 does not go less than about 3V higher than the negative supply voltage.
4) The LM358 has a low supply current. The 741 has a normal much higher supply current.
 
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Thread Starter

CircuitSurfer

Joined Sep 19, 2009
21
Thanks for your replies. This is just what I needed to get the confusion out. Will have to replace the 741 since it is so different than the 358. Howver I will still try to make the 741 work. I will post if it will succeed.
 
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Audioguru

Joined Dec 20, 2007
11,251
Instead of the LM358 I use similar but much better MC33171 single opamp, MC33172 dual opamps and MC33174 quad opamps.
The minimum supply voltage is also 3V and the maximum supply is higher on the new ones.
The inputs also work at the negative supply voltage.
The outputs also go to the negative supply voltage.
They have exactly the same low supply current.

But the old ones have horrible crossover distortion and the new ones don't.
The old ones have a poor response above 2kHz and the new ones go up fine to 35kHz.

I haven't used a 741 or LM358 opamp for about 40 years.
 
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