An improved bridge track-and-hold circuit

Abstract

The classic track-and-hold (T&H) circuits based on a diode-bridge feature known drawbacks: low-input impedance, limited slew-rate (SR) and input voltage swing, high-power consumption. To overcome those problems in this paper is proposed and analyzed a new T&H architecture. Tic diodes of the classic diode-bridge are replaced by transistors connected as emitter followers. Two buffers of unity-gain split up the bootstrap loop. PSPICE simulations with real transistor parameters demonstrate the advantages of the new circuit. The T&H waveforms of 5 MHz and 35 MHz input 2 V swing signal, sampled at 80 MHz, are shown. The results of slew-rate higher than 1400 V//spl mu/S, and power saving of above 10-20 times, compared with the conventional circuit, are obtained.