The 358's shall rule the night

[saturated]

I figured it was time to play with some of these guys especially since it aligns with the overall theme of this site 

Three specimens rescued from obscurity

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Kinda hard to read the top one

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Being intimidated by all the extraneous alpha numeric text I looked em up to see if there was really a difference

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Maybe there is but the pin out seems the same and the max voltage appears to be the same

This may be anti-climactic I think I just attach some DC voltage input a signal (or two) and watch it get bigger 

But with everything it's different to actually do it after reading about it and there is always stuff learn


One think I noticed is there can be a plus and minus Vcc or just a ground and positive Vcc
(Here we go again  )

[g1]

One think I noticed is there can be a plus and minus Vcc or just a ground and positive Vcc

If you use a single ended supply you have to use caps to block DC at inputs and outputs, as everything will run at 1/2 VCC. 
It's easier when you use a split supply, inputs and outputs will sit at zero VDC and you don't have to use caps there.

[Loudthud]

The LM358 or the LM324 (Quad version) don't sound the best for audio. You can make them sound a little better if you install a 1K resistor from the output to the negative supply. The best feature of this style opamp is that the input common mode range includes the negative supply. They do however go crazy (the output doesn't obey the inputs) if you allow the inputs to swing below the negative supply by more than about 0.3V so don't overdrive them.

[saturated]

Yes sir thanks 

This is turning out to be a good venture already because it's getting divergent all over the place

I looked in a book to see if they had some experiments and started to see all kinda stuff like slew rate and common mode rejection 

Anyhow they were using a 741 instead of a 358 so I looked further trying to avoid Google and came up with this

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My assumption that a 741 would be the same as a 358 just a tad different doesn't seem to hold up.

Anyhow i don't think I even have any 741s anyway 

I am interested in offset null whatever that is but I'm trying to keep things simple ATM

Something I really liked was it appears they wired a 741 in two different configurations so that the first is inverted (out of phase?)

And then the second it is non inverted

So I'm really interested in this maybe I can do a similar experiment with my 358.

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Glancing at the two I'm looking for differences I don't like how the polarity on 2 and 3 is reversed from top to bottom with really no other difference in power supply 

Ok aside from bypassing each side with resistors

Maybe I should get some 741s and others otw I think I'll order some tonight at work if you like some other ones lmk

BTW Happy Thanksgiving last Monday to our friends up north

 


Edit: ok just looked I actually do have some 318s and 741s

[Kaz Kylheku]

They do however go crazy (the output doesn't obey the inputs) if you allow the inputs to swing below the negative supply by more than about 0.3V so don't overdrive them.

Or use an inverting configuration that keeps the (-) input at a voltage very close to that of the (+) input at all times, which is held at ground (or your 1/2 Vcc). 

It's the non-inverting configurations that make the inputs swing with the signal, where issues are revealed when the inputs hit either rail.

[Loudthud]

Diagram B showing the non-inverting opamp is WRONG. The pin numbers on the inputs are in error. Feedback should always go to pin 2, the inverting input. The one exception to that rule is when you have some circuitry at the output of the opamp that inverts the signal.

[saturated]

Well wow all I got to say is you just never know man this is crazy

Before I did this I was thinking well ya know this is gonna be pretty anti climactic just hooking everything up and inputting a signal and ...... drum roll......oh looky there the output signal is bigger 
Cool experiment bro 

As usual I think I'm going to the corner store for a gallon of milk and end up in some crazy neighborhood with no lights 

Anyhow ok who wants some spaghetti 🍝

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I started out with plus and minus three volts and then plus and minus five volts and a randomly selected 6.2k resistor

Got this weird output (bottom)

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I tried a few things

Next I could hear JMF shouting "TURN UP THE Vcc DUMMY"  so I did that

And with that at least I could recognize a severely clipped square wave

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If you look at those little dots/nodes that was a middle for the square wave peaks and I could make either side diminish or even disappear by turning down either Vcc to make it lopsided

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Hmm now I hear someone else shouting oh it's G1 trying to tell me something about DC 

Anyway I'm about out of ideas ATM but one more thing

I tried repeatedly to decrease the input to get nice curved points on the square wave to make it a sin wave but it would just collapse and go to that weird rifle cartridge looking output 

Anyhow hope you guys are doing good 

[Loudthud]

You can't do much with opamps if you don't use feedback. Back to the textbooks !