Digital to analog converter system employing plural digital to analog converters which is insensitive to resistance variations

A digital to analog converter comprising:

• A. an amplifier circuit for generating said output signals having a voltage level determined by the voltage level of an input signal at an input terminal;
• B. a resistor network comprising:
• i. a plurality of series-connected resistors connected between a selected base voltage and said input terminal of said amplifier circuit, connections between each pair of resistors defining a node;
• ii. a plurality of depending resistors each having one terminal connected to a node;
• and
• iii. a plurality of switch circuits each having an input terminal connected to one of said depending resistors, each switch circuit being independently controllable to selectively connect said input terminal to said selected base voltage or to a selected reference voltage in response to a switch control signal;
• wherein, if the resistance value of each of said series-connected resistors and said depending resistors is defined in accordance with a base value of R and a tolerance of .epsilon., said series connected resistors each have a nominal resistance value R-.epsilon., and said depending resistors each have a nominal resistance value 2(R+.epsilon.).