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I want to use a rail-to-rail op-amp as a differential amplifier.

The op-amp is supplied by 3.3V and the input signals swings from 0 to 5V. I want the output to swing between 0 and 2.5V.

My question is if the schematic below safe, in the sense that the inputs of the op-amps will not see voltages higher than VCC+0.3V.

I assume it is as the positive side of the input signal goes through that voltage dividers but I am not sure.

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Why are you using a differential amplifier? What op-amp is it? \$\endgroup\$
    – Andy aka
    Mar 25 '20 at 16:04
  • \$\begingroup\$ I want to remove common mode noise and I cannot be sure that the negative side of the signal is truly at ground level. AD8628 \$\endgroup\$
    – Cez Chi
    Mar 25 '20 at 16:07
  • \$\begingroup\$ @Andyaka Oh yes, R4 should have been 5k as well. \$\endgroup\$
    – Cez Chi
    Mar 25 '20 at 16:15
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The input over-voltage section (page 17) in the data sheet says this: -

If inputs are subject to overvoltage, appropriate series resistors should be inserted to limit the diode current to less than 5 mA maximum.

Given that you are worried about protecting against over-voltage, the input resistors (R1 and R2) may be subject to a voltage difference of 5 volts - 3.3 volts = 1.7 volts. So, providing that R1 and R2 have a resistance of not less than 340 ohms you will be fine even if R3 and R4 went open circuit.

My question is if the schematic below safe, in the sense that the inputs of the op-amps will not see voltages higher than VCC-0.3V.

I believe you meant VCC + 0.3 volts.

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