FULLY BIPOLAR, 120-MSAMPLE/S 10-B TRACK-AND-HOLD CIRCUIT

This paper describes the design and experimental results of a fully bipolar track-and-hold (T&H) circuit for use in video applications. A fully differential, open-loop approach has been chosen in order to meet the specifications with respect to track-to-hold step, droop rate, and hold-mode feedthrough. In order to obtain maximum high-frequency performance, p-n-p transistors have been omitted from the design. The T&H circuit has been realized in a 3-GHz f(T) bipolar production process, with a minimum emitter size of 2 x 9-mu-m2. The die size is 0.25 mm2, consuming 40 mW from a single 5-V power supply. Ten-bit performance has been measured up to 120-Msample/s full-Nyquist sampling rate. At 200 Msample/s, 8-b performance has still been observed over the full-Nyquist band.