A 40 GS/s 4 bit SiGe BiCMOS flash ADC

This paper presents the design and experimental test of a 40 GS/s 4 bit single-core flash ADC in a 0.13 μm SiGe BiCMOS technology. The ADC exploits a traveling-wave concept and integrates a new low-complexity Pseudo-XOR gray encoder that makes use of folded-cascode differential logic. Up to a sampling rate of 39.04 GS/s the ADC provides a measured ENOB of more than 3 bits and a SFDR of more than 24.8 dBc within the frequency band from DC to 20 GHz. At 40.32 GS/s the frequency band for a minimum effective resolution of 3 bits is 12 GHz and at 42.24 GS/s it is about 5.3 GHz.