Maximum input signal of opamp and measuring signal volts

[preciousmolina666]

im going to build 2 stage gain, m using single supply 18
What is the maximum input of signal of opamp example 5532, does it list on datasheet?
and how to measure signal peak to peak using dmm

[ElectricDruid]

The maximum input signal depends on the gain, so it's not a fixed point. The maximum *output* signal is fixed, since that depends on the power supply. A typical op-amp will go to within a diode-drop or two of the rails in both directions, so say +/-13.7 volts on a +/-15V supply. But some op-amps manage to get within a single diode-drop, and then of course there are "rail to rail" op amps that get within millivolts.

How to measure P-P AC volts with a DMM? Dunno. You can't, easily. You can guesstimate by multiplying the number you get by 1.4, but that makes various assumptions about the wave shape.

HTH,
Tom

[preciousmolina666]

The maximum input signal depends on the gain, so it's not a fixed point. The maximum *output* signal is fixed, since that depends on the power supply. A typical op-amp will go to within a diode-drop or two of the rails in both directions, so say +/-13.7 volts on a +/-15V supply. But some op-amps manage to get within a single diode-drop, and then of course there are "rail to rail" op amps that get within millivolts.

oh the "gain" now i see, i just add x3 gain and my humbucker is still clipping a little

How to measure P-P AC volts with a DMM? Dunno. You can't, easily. You can guesstimate by multiplying the number you get by 1.4, but that makes various assumptions about the wave shape.

ive use a diy oscilliscope and sweep it 40hz to 2khz, measure it in ac its says 1.7 volts, in dc its says 9 volts ( output of opamp)

[GibsonGM]

I just use an oscillator (R.G.'s "less quick and dirty oscillator", in fact), and set it to .5V peak (1VP-P) with my oscilloscope.  Then I can see what's going on at the output and get a reasonable measurement.   Might try this at a little higher voltage, just to see about clipping and so on.
You can them plug your guitar in and get an approximation of ITS output by comparison.

This is just qualified by "so so volts @ 1kHz", which is where I set my oscillator to.  It is enough.   If you want more precision, you should probably get a signal generator...

[anotherjim]

If it's a non-inverting op-amp circuit, it's easy to forget the gain is +1 whatever the feedback resistor ratio is. Don't know if that's what's happening. Just that if Rf/Rin=3 then gain is x4, not 3. That itself should not clip an 18v circuit from a humbucker, however hot that is. If a second stage has the same mistake - the 2 stage gain is multiplied together which might clip.

On the datasheet, common mode input voltage range is the nearest clue to input range. It suggests the inputs should not go within 3volts of the + or - supply pins. Actually says +12 or -12v with +/-15v dual supply.

[PRR]

> measure P-P AC volts with a DMM? ... by 1.4

No, 2.8.

And as you say, this has a "sine" assumption in it.

This is actually not-far-out for any likely audio waveshape. You have to go to very narrow pulses to get 20% error. As speech/music audio is all-over anyway, 20% is not a big deal.

The old VTVMs actually measured P-P then divided by 2.8 to read "sine RMS". Very handy in audio clipping work. You could DIY a P-P catcher. But with the very variable nature of guitar, I don't think this is any better than using 3X on the "rms" reading.

[EBK]

> measure P-P AC volts with a DMM? ... by 1.4

No, 2.8.

And as you say, this has a "sine" assumption in it.

This is actually not-far-out for any likely audio waveshape. You have to go to very narrow pulses to get 20% error. As speech/music audio is all-over anyway, 20% is not a big deal.

The old VTVMs actually measured P-P then divided by 2.8 to read "sine RMS". Very handy in audio clipping work. You could DIY a P-P catcher. But with the very variable nature of guitar, I don't think this is any better than using 3X on the "rms" reading.

I need to grow up.  I chuckled at "P-P catcher". 

[ElectricDruid]

> measure P-P AC volts with a DMM? ... by 1.4

No, 2.8.

And as you say, this has a "sine" assumption in it.

Ah, my mistake. You're quite right. Not thinking clearly.

This is actually not-far-out for any likely audio waveshape. You have to go to very narrow pulses to get 20% error. As speech/music audio is all-over anyway, 20% is not a big deal.

Well, speech and music is one thing. I can easily get a narrow pulse out of my old analog synth, although maybe that's closer to "test signal" generation than you're thinking of. But I tend to think of analog synth shapes first and speech a long time after.

T.

[preciousmolina666]

Just that if Rf/Rin=3 then gain is x4, not 3.

oh thanks

> measure P-P AC volts with a DMM? ... by 1.4
No, 2.8.
And as you say, this has a "sine" assumption in it.

yey im close

power supply LM317 = 19.3V (no load)
xr2206 oscillator (calibrated) = 1.5V sinewave
input to 5532 non inverting (1k and 2.2k) =5.3volts = 14.84 VPP (without clipping)
if 5.5 V the lower side of wave begin to clip
if 5.7 V upper side begin to clip too

so my max is 14.84 VPP this is normal?

[PRR]

> power supply = 19.3V
> max is 14.84 VPP

You can not put the output ALL the way to the rails. The internal transistors won't go to zero voltage drop.

19.3V-14.84V= 4.5V less than the supply, or 2.25V each side. This is not unreasonable for conventional opamps. A "perfect" opamp on 19V supply would not make appreciably bigger signals.

> 1.5V sinewave
> non inverting (1k and 2.2k) =5.3volts

Gain is 3.2. And 1.5V times 3.2 is 4.8V, a small difference from your 5.3V number.

> so my max is 14.84 VPP this is normal?

For Guitar Cord work, 15Vpp or 5Vrms is Real Frikkin Big.

Hi-Fi and PA work rarely beats 2V. (Larger signals INside many mixing consoles, and possible at outputs, but nearly no next-box ever needs that much.)

Why do you need so much signal? NO input needs that much. 2V maybe 2.8V will slam any power amp. Less than 1V will slam any guitar amp.

[preciousmolina666]

>Why do you need so much signal? NO input needs that much. 2V maybe 2.8V will slam any power amp. Less than 1V will slam any guitar amp.

im doing some record, i got noise maybe because of my audio interfac , its -80db white noise, my humbucker is at -3db only because preamp opamp clipped it, i want to amplify until my own noise is more than -80db or atleast i need more 2-3db