Show how to make a two-digit digital-to-analog converter by appropriately scaling the input resistors of a summing amplifier. The digital input represents two digits, each consisting of four lines that represent the values 1, 2, 4, and 8 for the respective digits. An input line is either at +1 volt or at ground, ie, the eight input lines represent 1, 2, 4, 8, 10, 20, 40 and 80. Because op amp outputs generally do not swing beyond +- 13 volts, you will have to settle for an output in volts equal to one-tenth the value of the input number.