A 10-B 50 MS/S 500-MW A/D CONVERTER USING A DIFFERENTIAL-VOLTAGE SUBCONVERTER

A BiCMOS A/D converter using a ''differential voltage subconverter,'' which directly converts a voltage difference of complementary analog inputs to a digital code, is described. Fully differential architecture has advantages in immunity of common-mode error and in reduction of supply voltage. This differential-voltage subconverter realizes the fully differential A/D conversion without using interpolation technique. This subconverter is free from CR delay caused in the ladder resistors. Circuit techniques for high-accuracy conversion with single 5-V power supply, such as compensation technique for VBE modulation in emitter degeneration amplifier, are also described. A 10-b A/D converter is fabricated in a 0.8-mum BiCMOS process with f(T) of 9 GHz. It successfully operates at 50 MS/s with 500-mW power consumption and with 5-V single supply.