I have created a simple non inverting voltage follower with single supply of 3.3 V. I have created two cases of input voltages. Case 1: AC Amplitude 0.25 mV, Case 2: AC Amplitude 1 V. Both cases are working at a DC Offset of 1.25 V and a frequency of 100 KHz.
In both cases the output fails to track the input voltage accurately. In case 2, the maximum rate of rise of voltage can be calculated as V*2*pi*f which comes out to 0.628 V/us which is less than the specified slew rate of 1 V/us. In case 1, the maximum input rate of rise of voltage is much lesser than the specified slew rate and still the opamp fails to track the input.
In both cases I have measured the achieved slew rate of the OPAMP which comes out to 0.07 V/us (+/- 0.01 due to measurement error), again much lesser than the specified slew rate of the IC.
Why is this occurring? What are the factors that play into calculating the required bandwidth of an OPAMP.? A glance at datasheet would suggest at least a 1 MHz bandwidth at unity gain at 3 V supply. However, the simulations do not seem to bear out this fact. Am I missing something about how OPAMPS work? Please explain this phenomena.
I have attached the relevant Spice files and images for your reference.
Thanks,
Steven
