International Journal on Advanced Science, Engineering and Information Technology, Vol. 8 (2018) No. 3, pages: 924-929, DOI:10.18517/ijaseit.8.3.4329

A Simple Transistors Width Adjustment Method on CMOS Transmission Gate Switch to Reduce Hold Error of S/H Circuit

Abstract

Sample and Hold (S/H) circuit is one of the most important circuits in analog and mixed signal integrated circuit. This circuit is the main block of many applications, such as switched capacitor circuit, analog to digital converter (ADC), etc. The majority of S/H circuits are implemented using MOS technology because the high input impedance of MOS devices performs excellent holding functions. Ideal characteristics of the S/H circuit are low hold error, low On-resistance and constant On-resistance in all voltage levels. There are some techniques to reduce the hold error and achieve low On-resistance. However, these techniques need additional compensation circuit. For this reason, a simple transistors width adjustment method on CMOS transmission gate (TG) switch to reduce hold error of S/H circuit without additional circuit that can be implemented in the actual design process is proposed in this paper. The basic idea of the proposed method is balancing hold error caused by N-type and P-type MOS transistor in CMOS switch that is used in S/H circuit. The performance of the proposed method is evaluated using HSPICE with 0.6 µm CMOS standard process. As a result, using 1.5 V constant input in the PMOS transistor width W_P range of 3 to 35 µm the average W_N/W_P ratio given by this proposed method is 0.928 with the average absolute hold error is 0.427 mV and maximum absolute hold error is 0.8 mV.

Keywords:

sample and hold circuit; hold error; hold error reduction; CMOS switch; clock feedthrough; channel charge injection.

Viewed: 1174 times (since abstract online)

• Show fulltext