Low-power analog-to-digital converter

An A/D converter for outputting a digital signal of m+n bits, comprising:

• folding circuits for being supplied with differential analog signals and for outputting higher m bits of said digital signal respectively;
• sine wave generators for being supplied with said differential analog signals and for outputting lower n bits of said digital signal respectively;
• and
• a current interpolation circuit for interpolating outputs of said sine wave generators;
• said folding circuits including:
• at least one differential MOS transistor pair having gates supplied with differential voltage pairs which are differences between said differential analog signals and differential reference voltages, respectively;
• a current source for supplying a first current to said differential MOS transistor pairs;
• and
• a current mirror circuit for supplying a second current to a pair of current channels;
• wherein drains of said differential MOS transistor pairs are cross-connected alternately to said pair of current channels so that folded differential current pairs are outputted from ends of said pair of current channels.

An A/D converter for outputting a digital signal of m+n bits, comprising:

• folding circuits for being supplied with differential analog signals and for outputting higher m bits of said digital signal respectively;
• sine wave generators for being supplied with said differential analog signals and for outputting lower n bits of said digital signal respectively;
• and
• a current interpolation circuit for interpolating outputs of said sine wave generators;
• said sine wave generators including:
• a plurality of differential MOS transistor pairs having gates supplied with differential voltage pairs which are differences between said differential analog signals and differential reference voltages, respectively;
• a current source for supplying a first current to said differential MOS transistor pairs;
• and
• a current mirror circuit for supplying a second current to a pair of current channels;
• wherein drains of said differential MOS transistor pairs are cross-connected alternately to said pair of current channels so that sine wave currents are outputted from ends of said pair of current channels.