A 10-GS/s 8-bit SiGe ADC with Isolated 4×4 Analog Input Multiplexer

In this paper, a time-interleaved 10GS/s 8bit ADC fabricated in 0.18μm SiGe BiCMOS technology has been demonstrated. The proposed 4×4 input multiplexer allows the ADC to support 1/2/4-channel sampling modes with no compromised isolation and input bandwidth. In the THA stage, a switched emitter follower (SEF) topology with delayed dummy clock is introduced to minimize the output overshot effect of the SEF. The measurement result shows that the ADC has a SFDR >43dBc over the entire Nyquist frequency. It has an effective number of bits (ENOB) about 6.6 at low frequency and dropping to 5.5 at 5GHz.