I am going to choose an op-amp as a buffer for my pH sensor. How much slew rate of an op-amp is important in choosing my op-amp?
The slew rate of op-amp that I search range from 0.02 V/µs to 12 V/µs.
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4\$\begingroup\$ How fast does the pH change?? \$\endgroup\$– user16324Commented Mar 12, 2017 at 13:49
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1\$\begingroup\$ It's only relevant for large high frequency signals, or step responses \$\endgroup\$– D.A.S.Commented Mar 12, 2017 at 14:15
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2 Answers
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You only need to worry about slew rate for quickly changing signals, like audio for instance.
pH measurements change so slowly that you can ignore slew rate, and choose the amplifier on power consumption or price.
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1\$\begingroup\$ For pH, lowest bias current or highest input impedance would probably be better metrics. \$\endgroup\$ Commented Nov 13, 2017 at 23:41
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For non-sinusoidal sources, I always heard it used for capacitive input filtering, since the slew-rate acts like the leading edge of a sine wave. If your signal remains 12V, your slew-rate resembles a 1MHz input wave. If you only need 1V, your slew-rate behaves like the leading edge of a 12MHz leading edge (roughly). So in that case you could use a smaller capacitor to not dampen the source signal.