A 10 Gsamples/s SiGe Track-and-Hold Amplifier with 8-bit Resolution

The Track-and-Hold Amplifier (THA) practically accounts for most of the dynamic parameters of an ADC and hence optimization of its performance is crucial. This paper presents the design of a bipolar Track- and-Hold Amplifier (THA) capable of operating at 10 Gsamples/s and suitable for use with analogue-to-digital converters with a resolution of up to 8-bits. The high sampling rate prevents the use of classical feedback techniques for linearization and error compensation. This implies that the linearity of the high speed THA relies mostly on the intrinsic properties of the devices and on minor feedback constructions such as emitter degeneration of the input buffer. The THA was implemented using a 0.25 mum SiGe BiCMOS process, featuring npn devices with an f_T of 50 GHz. Simulation results detailing the transient response, linearity, frequency response and harmonic distortion are presented.