Digital to analog converters (DACs) convert digital signals or numbers to analog voltages. In some embodiments, a digital processor outputs a stream of numbers, such as binary numbers to a DAC. The DAC converts the numbers to an analog signal. For example, in digital audio, audio signals are processed using digital electronics, however, the digital signals need to be converted to analog signals in order to be heard by a user.
Because the input signal to a DAC is a digital signal having discrete values, the analog signal output by the DAC has a discrete number of voltage levels. For example, a four bit DAC may be able to receive inputs of sixteen different values, which corresponds to sixteen discrete voltage levels output by the DAC. Some DACs fine tune the output voltage by adjusting bias voltages to the DAC. These fine tuning mechanisms require the use of many resistors and switches and, as a consequence, use a large area on the DAC. They also subject the DAC to slower speeds due to the parasitic capacitance associated with the resistors.