Apparatus and methods for actively terminated digital-to-analog conversion

摘要

Apparatus and methods for digital-to-analog conversion are disclosed. In one embodiment, an electronic system includes a bias circuit and a digital-to-analog converter (DAC) including an input that receives a digital input signal and an output that drives a transmission line. The digital input signal can be used to control a magnitude and polarity of an output current of the DAC. The DAC further includes one or more p-type metal oxide semiconductor (PMOS) termination transistors that receive a first bias voltage from the bias circuit and one or more n-type metal oxide semiconductor (NMOS) termination transistors that receive a second bias voltage from the bias circuit. The bias circuit controls the voltage levels of the first and second bias voltages to control the termination transistors' small signal resistance to actively terminate the DAC's output.

主权项

1. An apparatus comprising:
a first digital-to-analog converter (DAC) including a data input configured to receive a digital input signal and an output configured to generate an output current, wherein the first DAC comprises an active termination circuit including one or more p-type metal oxide semiconductor (PMOS) termination transistors and one or more n-type metal oxide semiconductor (NMOS) termination transistors; and a bias circuit configured to generate a first bias voltage and a second bias voltage, wherein the first bias voltage is configured to control a small signal resistance of the one or more PMOS termination transistors, wherein the second bias voltage is configured to control a small signal resistance of the one or more NMOS termination transistors, and wherein the one or more PMOS termination transistors and the one or more NMOS termination transistors provide active termination to the output of the first DAC.