A 70 GHz Small-signal Bandwidth 40 GS/s Track-and-Hold Amplifier in 130 nm SiGe BiCMOS Technology This paper presents a broadband track-and-hold amplifier (THA) based on switched-emitter-follower (SEF) topology. The THA exhibits a record 3dB small-signal bandwidth of 70 GHz. With the high sampling rate of 40 GS/s, it achieves an effective number of bits (ENOB) of 7.5 bit at 1 GHz input frequency and an ENOB of >5 bit up to 15 GHz input frequency. The chip was fabricated in a 130 nm SiGe BiCMOS technology from IHP (SG13G2). It draws 110 mA from a -4 V supply voltage, dissipating 440 mW.