The Evaluation of Device Model Dependence in the Design of a High-Frequency, Analog, CMOS Transconductance-C Filter

• Main Author: Brotman, Susan Rose
• Format: Others
• Published: PDXScholar 1994
• Subjects: Electric filters > Design and construction; Integrated circuits > Design and construction; Computer-aided design
• Online Access: https://pdxscholar.library.pdx.edu/open_access_etds/4701; https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=5772&context=open_access_etds

It is important to have the ability to predict the effects of device model variation when designing integrated transconductance-C type active filters. Applying these filters to integrated circuit design has become increasingly popular due to its ease of implementation in monolithic form. With the introduction of fully automated design tools, predictable behavior of high-level variables becomes still more important. The purpose of this study is to evaluate the process parameter spread of analog device models to determine the effect on the design parameters of an active filter. This information's significant contribution directly effects the feasibility and realization of automating analog filter design. In order to explore the dependence of filter performance on the device v model parameter spread, a fifth-order inverse Chebyshev filter is designed and simulated using a two year history of process models. It has not been observed that higher order filters have been successfully designed using fully automated design tools. This filter was realized using automated filter design currently being developed in parallel with this study. A single-ended input to single-ended output transconductance amplifier is chosen for this design for its simplicity and small size. Differential performance is easily adapted with exact duplication which is demonstrated in the measurements of the fabricated filter. Simulation of the design is performed using MOSIS SCNA device parameters. Filter performance data such as cutoff frequency, stopband attenuation, and phase response is collected. Experimental results from the fabricated device are compared to simulation and the original prototype. 2 It is shown that the most predicable effect on the design parameters of a filter is caused by the parasitic output conductance parameter g0. This process dependent variable causes both a deviation in the cutoff frequency, and a decrease in the filter quality factor. In addition, it is also shown that the practice employed to predistort for absorption of parasitic capacitors in a MOS technology is a very effective tool in the reduction of capacitive process dependence.n software