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Experiment VIII Sensitivity analysis for ADC using OPAMP.
The flash type A to D converter is based on comparing and unknown analog input voltage with a set of reference voltages. To convert an analog signal in to a digital signal of n-output bits (2n-1) number of
Comparators required for 2-bit ADC three comparators required.
As shown in figure the three Op-Amps are used as a comparator. The non-inverting inputs of all comparators are connected to the analog input voltage. The inverting input terminals are connected to a set of reference voltages V/4, 2V/4 and 3V/4 respectively, which are obtained using a resistive divider network and power supply. The output of comparator is in positive saturation state when the voltage at the NIV terminal is more than the voltage at INV terminal and it is in negative saturation state otherwise. When the analog input voltage is less than V/4, the voltage at the NIV terminals of the three comparators is less than their respective INV input voltages and hence the comparator outputs are C1, C2, C3=000.When the analog input is between V/4 and V/2, the comparator outputs are C1, C2, C3=100.Following table shows comparator outputs of different ranges of analog
voltage and their corresponding digital outputs.
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