Digital-to-analog converter for video application

Abstract

A digital-to-analog converter comprises a current source for supplying a current of predetermined magnitude to a circuit node, and a switch connected to the circuit node, and defining a first current path leading to a reference potential terminal and a second current path leading to an output terminal. The switch has an input terminal, at which it receives a first digital signal of one binary digit for conversion to analog form, and also has a reference terminal, and has a first condition, when the voltage at the reference terminal is higher than that at the input terminal, in which the current supplied to the circuit node is delivered to the output terminal, and a second condition, when the voltage at the reference terminal is lower than that at the input terminal, in which the current is delivered to the reference potential terminal. The converter also comprises a level shifting network which receives a second digital signal of one binary digit and generates an output signal having a voltage that depends on whether the second digital signal is a logical zero or a logical one; this output signal is applied to the switch's reference terminal. If the second digital signal is a logical zero, the voltage of the output signal lies intermediate the voltage levels corresponding to the first signal's being a logical zero and a logical one, and if the second digital signal is a logical zero, the voltage of the output signal is higher than the voltage level corresponding to the first signal's being a logical one.