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What are the drawbacks of this design vs a design like the TI one here?

Should the feedback be on the other side of R2?

Are there any other gotchas using something like this, vs limiting using a 7v+- supply?

The purpose of this limiter is to prevent overdriving of a PCM1862 audio adc.

enter image description here

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  • \$\begingroup\$ Statically, I see no difference, but since the ADC has some input capacitance, connecting the feedback on the other side slows down the system a bit. \$\endgroup\$ – Vladimir Cravero May 29 '17 at 12:52
  • \$\begingroup\$ That is a horrible schematic, not a good way to tell what Vcc is \$\endgroup\$ – Voltage Spike Nov 4 at 17:02
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    \$\begingroup\$ This question is over two years old. Anyway, Whats unclear about 17+ and -17? \$\endgroup\$ – Erik Friesen Nov 4 at 20:25
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The feedback is after R2 to ensure that the lighter effects of the zener (a volt or so below the "official" knee voltage) do not distort the waveform too early on.

You could use a R2R op-amp but there might be "nuances" as it comes out and goes into output saturation that might not be as significant using the zener method.

The TI method also uses the zeners within the feedback loop and will behave fairly similarly but is more sophisticated in that the clipping points are controlled by a potentiometer.

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1 - If you're going to use +/- 7 volt supplies, and you want to limit the ADC input to +/- 7 volts, why bother with all this stuff? Make a simple follower with (let's say) a 1k input resistor, as you have shown. With +/- 7 volts on the op amp, you cannot put out more than +/- 7 volts. If you're worried about high input voltages brute-forcing through the op amp, use a divide by two voltage divider and a x2 amplifier setup, like

schematic

simulate this circuit – Schematic created using CircuitLab

2 - Why do you think that a +/- 7 volt supply will let the 5532 put out +/- 7 volts? This ability would make the 5532 a RRO (rail-to-rail output) op amp, and it most assuredly is not. If you look at the data sheet you'll see that, for +/- 15 volt input, the ouput swing (Vopp) is only guaranteed to be about 24 volts, with 26 as typical. This suggests that the output will only swing to within about 2 volts of the supplies, which would give you +/- 5 volts. You really need to be careful in trying to estimate this, since the figure is not specified for other supply voltages. Experimentation is definitely called for.

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