A high speed high dynamic range track-and-hold amplifier (THA) using 0.18 μm SiGe process is presented in this paper. A differential feedthrough cancellation technique is proposed to enhance the hold-mode isolation and linearity of the THA. The measured spurious free dynamic range (SFDR) is up to 55 dB with a sampling rate of 16 GS/s. The measured input bandwidth is up to 8 GHz with a hold-mode isolation of higher than 50 dB. The total DC power consumption is 132 mW with a supply voltage of 2.5 V. The chip size is 1.3×0.89 mm2. As compared to the advanced silicon-based THAs, this work features high isolation, high speed, low dc power, good SFDR and linearity.