Optimum swing at input to first opamp
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7 years 5 months ago - 7 years 5 months ago #611
by sanantonioglamour
Optimum swing at input to first opamp was created by sanantonioglamour
What would the optimum AC voltage be at the input to the first opamp? I guess the optimum output is 5vpp, is that correct?
Last edit: 7 years 5 months ago by sanantonioglamour. Reason: typo's and additional info
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7 years 4 months ago #617
by Ray
Replied by Ray on topic Optimum swing at input to first opamp
Having a look to the
TL972 datasheet
you can see that the input voltage range (page four) is:
VCC– – 0.3 and VCC++ 0.3
so if you are powering at 5V, the optimum input voltage is 5V - (2*0.3) = 4.4Vpp
VCC– – 0.3 and VCC++ 0.3
so if you are powering at 5V, the optimum input voltage is 5V - (2*0.3) = 4.4Vpp
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7 years 4 months ago #648
by sanantonioglamour
Replied by sanantonioglamour on topic Optimum swing at input to first opamp
I see thanks. I am only geting 2.5volts at the output of the opamp before clipping starts to occur. clipping ocurs at the top first. The bottom of the signal increases about another volt before it too clips. any ideas?
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7 years 4 months ago #653
by Ray
Replied by Ray on topic Optimum swing at input to first opamp
you are using the TL972 op amp, arent you?
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7 years 4 months ago - 7 years 4 months ago #654
by sanantonioglamour
Replied by sanantonioglamour on topic Optimum swing at input to first opamp
no, LM358. I suppose that's the reason.
I tried a MCP 602 and that gets 4 or so, volts swing. Can you tell me what the difference is. I mean what should I be looking for on the datasheet? thanks
I tried a MCP 602 and that gets 4 or so, volts swing. Can you tell me what the difference is. I mean what should I be looking for on the datasheet? thanks
Last edit: 7 years 4 months ago by sanantonioglamour. Reason: adding comments
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7 years 4 months ago #655
by Ray
Replied by Ray on topic Optimum swing at input to first opamp
I have checked the LM358 datasheet:
www.ti.com/lit/ds/symlink/lm358.pdf
And the input voltage levels (Vcir) should be between VCC -2V, so powering at 5V, the input voltage swing goes from 0 to 3V, so the clipping you see could be normal, we choose the TL972 because it is rail-to-rail and admits a wider range of input voltages.
I would suggest you to adjust the VR1 input trimmer so the guitar input levels stays between 0 and 3V.
Every op amp datasheet sates the input voltage swing in a different way, the TL972 has a graph on page 4, the LM358 call it ""Common-mode
input voltage range", etc
www.ti.com/lit/ds/symlink/lm358.pdf
And the input voltage levels (Vcir) should be between VCC -2V, so powering at 5V, the input voltage swing goes from 0 to 3V, so the clipping you see could be normal, we choose the TL972 because it is rail-to-rail and admits a wider range of input voltages.
I would suggest you to adjust the VR1 input trimmer so the guitar input levels stays between 0 and 3V.
Every op amp datasheet sates the input voltage swing in a different way, the TL972 has a graph on page 4, the LM358 call it ""Common-mode
input voltage range", etc
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7 years 4 months ago #660
by avasmith
Hello brownt, did it work with a LM358? if so, could you please tell me if i needed some special arrangement?
thanks a lot!
Replied by avasmith on topic Optimum swing at input to first opamp
brownt wrote: no, LM358. I suppose that's the reason.
I tried a MCP 602 and that gets 4 or so, volts swing. Can you tell me what the difference is. I mean what should I be looking for on the datasheet? thanks
Hello brownt, did it work with a LM358? if so, could you please tell me if i needed some special arrangement?
thanks a lot!
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7 years 4 months ago #662
by sanantonioglamour
Replied by sanantonioglamour on topic Optimum swing at input to first opamp
I don't know a lot about these things, but it seems that the output swing was limited to about 2.5volts with the LM358, and the gain seemed low. I changed R4 from 4K7 to 1K to increase the gain. But in the end I used a MCP602 and the swing changed to about 4 volt peak to peak.
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