An improved switched-emitter-follower for high-resolution GS/s-rate track-and-hold amplifiers

This paper presents an improved switched-emitter-follower for high-resolution GS/s-rate track-and-hold amplifier. A dummy switched-emitter-follower is introduced to compensate track-mode nonlinearity. And a clamping amplifier is utilized to reduce hold-mode feedthrough in high sample rate. The proposed switched-emitter-follower was chip verified in a 12bit 1GS/s THA based on 0.18pm SiGe BiCMOS process. Post-layout simulations show that the proposed THA achieves a spurious free dynamic range of 71 dB for 497 MHz input frequency at 1 GS/s rate. Operating from a 3.3V supply, the power dissipation of the proposed switched-emitter-follower is 156mW.