fast analog to digital converter - for frequencies up to 500 kHz

for frequencies up to 500 kHz The design for a fast analogue to digital converter shown here clearly shows that this type of circuit does not necessarily have to be com- plicated. Instead of the usual sawtooth generator + comparator + counter + oscillator, we have used a system in which a fixed reference voltage is fed to a number of com- parators. This is known as a parallel converter. The delay normally in- troduced by the counting process is done away with so the whole pro- cess is very fast. The disadvantage of this set-up is the large number of components as each step requires a comparator but, in the three-bit example here, that is not a problem. The reference voltages for the various comparators are generated by means of a series of 1% resistors and a current source based on T1. The conversion factor is set with P1 (Uref = 1.5 . . . 9 V). The analogue input voltage is fed via buffer stage IC4 to the inverting inputs of Al . . . A8. A priority encoder is used for the convers...