ua741

That doesn't sound right.

Post your circuit?

Are you sure that your power supply voltages are actually getting to the chip? Is it properly bypassed? Could it be any other common weirdness that just happens to be showing low slew rate as a symptom?

--
www.wescottdesign.com

Are you applying any feedback? It sounds like you are trying to operate it open loop.

At 100 Hz the open loop gain should be about 100 times and, 5mV should give about 500mV out, open loop.

However, the DC input offset voltage and offset current could easily drive the open loop amp output into one of its rails causing virtually no AC out.

Connect the amp as a gain of 10 with a 1k input resistor and a 10k feedback resistor to the neg input, ground the pos input and be sure there is a DC path to ground through your source and try again.

"Bob is too Eld"

** Err - the open loop gain of a 741 is 10,000 times at 100Hz. ** No need for a DC path exists when the pos input is grounded cos the feedback loop will make sure the neg input is within 1 mV of the pos one.

... Phil

DC

Your right....I had a brain-fart and figured it wrong. For some reason I can't seem to divide a million by 100. Oh well, the fact remains that the OP must be trying to run the amp open loop.

"Bob Elderly"

** The OP is probably a congenital half wit making the dumbest of errors with a basic simulator.

Die of fright if he ever saw a * REAL * uA741 ....

..... Phil

It would be nice if you can show us your attempted circuit?

Open loop gain of a 741 would give you a rail to rail square wave on the output. You have to be limiting the gain external to the op amp or your measuring method or instrument is wrong.

A 741 won't do Rail TO Rail. I think the fact it does square wave in an open loop is what you're trying to convey in this situation.

To be honest, I haven't really found a spec anywhere that signifies what Rail to Rail is. Every chip i've spec'ed as being rail to rail, never reached it's actual rail voltages in the data sheet. So some where, some one has decided what constitutes a rail level output and what does not. Compared to what RR types do that are currently out there, the 741 does not fall into that category.

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ck

Thank you all. It's set up as simple inverter, with (+) pin to ground via same R as the input R and only 100Hz.

Still working on it, but I replaced the F/B circuit with only 10ohms (R) between signal and (-) pin, and 1000k between (-) pin and output, for closed loop gain 100x and it worked. So it seems that I need low R at (-) input terminal. You see, I had been using R=3D1k and the feedback R=3D100k.

Now, my fcn generator has about 700 o/p impedance. Does that matter?

I had similar problem with AD8620 and CA3140...still working on them.

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DC

cc, Sorry did I understand that correctly, you've got 10 ohms and 1 Meg ohm (1000k)

That's a gain of 10^5. Yeah! it aint gonna work at 100 Hz.

George H.

OK, guys.....my bad.............

I thought I had checked this first when I began using my (cheapo) fcn. generator, but I was getting about 2.5v dc bias on which I was riding

2-5mv signal, so of course i couldn't get much gain with the +/- 12v supply(or 9 depending on my mood that day). All I got was flatline or noise when trying for even 10x gain.

Sorry for the fuss, but I'm learning at home.....I'm lucky I found a deal on an old Tek 7633 and I can even see the waveforms at all. This is how we learn.......sometimes with help from others.

Lesson, check all the supposedly obvious solutions first.

CC

Have you seen that magical smoke yet?

One thought, just don't let it escape.

Ditto that. "rail to rail," if specified, doesn't meet full specifications at the rail extremes.

figure of speech.