Switching dac pulse encoding circuit

A digital-to-analog converter (DAC) for converting a differential digital signal to a representative analog signal, said differential digital data signal including a positive part and a negative part, said converter comprising:

• a first switch responsive to the digital signal, said first switch including a differential transistor pair having a first transistor and a second transistor;
• a delay device responsive to the digital signal, said delay device delaying the digital signal one-half of a period of a predetermined clock signal;
• a second switch responsive to the delayed digital signal from the delay device, said second switch including a second differential pair of transistors having a third transistor and a fourth transistor;
• a current source for generating a current signal;
• and
• a third switch responsive to the current signal from the current source and the clock signal, said third switch including a third differential transistor pair having a fifth transistor and a sixth transistor, said clock signal having clock cycles defined by a positive portion and a negative portion, wherein the third switch directs the current signal from the current source to the first switch during the positive portions of the clock cycle and directs the current signal from the current source to the second switch during the negative portions of the clock cycle, and wherein the first switch directs the current signal to a first output of the DAC during the positive portions of the clock cycle when the digital signal is transmitting a one bit, the second switch directs the current signal to the first output of the DAC for the negative portions of the clock signal when the digital signal is transmitting the one bit, the first switch directs the current signal to a second output of the DAC for the positive portions of the clock cycle when the digital signal is transmitting a zero bit, and the second switch directs the current signal to the second output of the DAC for the negative portions of the clock signal when the digital signal is transmitting the zero bit.

A method of converting a digital signal to an analog signal, comprising:

• applying a digital signal to a first switch;
• delaying the digital signal by a predetermined period of time;
• applying the delayed digital signal to a second switch;
• generating a current signal;
• applying the current signal and a clock signal to a third switch, said clock signal having clock cycles defined by a positive portion and a negative portion;
• directing the current signal from the current source to the first switch during the positive portions of the clock cycles;
• directing the current signal from the current source to the second switch during the negative portions of the clock cycles;
• directing the current signal from the first switch to a first output when the digital signal is transmitting a one bit;
• directing the current signal from the second switch to the first output when the digital signal is transmitting the one bit;
• directing the current signal from the first switch to a second output when the digital signal is transmitting a zero bit;
• and
• directing the current signal from the second switch to the second output when the digital signal is transmitting the zero bit.