Patent ID: 7417572

Claim:
An electrical circuit comprising: a plurality of current control devices commonly interconnected at first terminals thereof and commonly interconnected at second terminals thereof, each of said current control devices having an amount of electrical current flowing therethrough proportional to a voltage applied to respective control terminals thereof; a plurality of switching devices selectably coupling said respective control terminal of each of said current control devices to one of an upper reference voltage and a lower reference voltage, said switching devices are connected electrically in series one with another to form a switching device chain, said first reference voltage and said second reference voltage being respectively applied to first and second terminal ends of said switching device chain, said control terminal of each of said current control devices being electrically coupled to said switching device chain between a respective pair of said switching devices thereof, said switching devices in said switching device chain are arranged into a set of rows and a set of columns such that all of said switching devices respectively in each of said columns are mutually activated into one of a conducting state and a non-conducting state by a signal on a common control line; a row selection switching device electrically coupled to said switching device chain at each of said sets of rows thereof so as to provide a short circuit path around all of said switching devices respectively in each of said sets of rows when said corresponding row selection switching device is activated into a conducting state; and an output node coupled to said commonly interconnected second terminals and to a constant current source and providing thereby a voltage between said upper reference voltage and said lower reference voltage proportional to a number of said current control devices coupled to each of said upper reference voltage and said lower reference voltage.