Can opamps work with signal that may go higher or lower than supply voltage?
The answer is "no" and "yes".







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. (a) Voltage follower. (b) Voltage divider and follower. (c) Inverting amplifier.


(a) Since the IN signal is connected directly to the op-amp non-inverting input it is not allowed to exceed the input voltage limits. Usually that means keeping within the supply rail voltages.
(b) By adding a divider in front the amplifier can now handle very large voltages - eleven times higher in this case.
(c) In the inverting mode the signal can be attenuated by increasing the input resistor. Gain in this case is -0.1 so the input could go to ten times the supply rail voltage for a rail-to-rail op-amp.


Note that (a) doesn't load the input signal due to the very high input impedance of the op-amp. (b) and (c) do load the IN signal. Whether this is important to you or not depends on the preceding circuit.