Patent ID: 7403178

Claim:
A source driver circuit for an active matrix electroluminescent (EL) display, comprising: a shift register circuit for receiving a main clock signal and generating an enable signal for sequentially storing a digital data; a line latch circuit for sequentially storing the data by the enable signal, and outputting the stored digital data, in parallel; a digital-to-analog converter/ramp circuit for converting the digital signal, which is outputted from the line latch circuit, to an analog signal, and at this time, generating a ramp signal, simultaneously, the digital-to-analog converter/ramp circuit further comprising: a resistor-string comprising a plurality of nodes between power supply terminals, a given voltage difference existing therebetween; a digital-to-analog converter (DAC) switch unit in which each of DAC switches is connected to each of the nodes in the resistor-string; a digital decoder arranged to receive the digital data and generate a signal that controls each of the switches; and a ramp switch unit in which each of ramp switches is connected to each of the nodes in the resistor-string; an output buffer circuit for inputting the converted analog data; and a ramp signal that is independent of a change of temperature or a threshold voltage; wherein each of the ramp switches is a MOS device; and wherein each MOS device has its gate driven by a separate ramp switch control signal; each MOS device source input is connected to a different node of the resistor-string; and drains of the MOS device are connected together to generate the ramp signal.