Showing papers by "David A. Hodges published in 1979"
01 Jan 1979
TL;DR: In this paper, the basic operation of switched-capacitor filters is reviewed, followed by a discussion of the properties of the various circuit building blocks in MOS technology, and a summary of several filter organizations which appear to be well suited to switch-capACitor implementation is presented.
Abstract: In the past several years, much progress has been made in bringing the economies of integrated-circuit technology to bear on the realization of voiceband frequency selective filters. This paper will review one approach to this problem, the use of switched-capacitor techniques. The paper emphasizes the practical aspects of switched-capacitor filter design under the constraints imposed by MOS integrated-circuit technology. The basic operation of switched-capacitor filters is reviewed, followed by a discussion of the properties of the various circuit building blocks in MOS technology. Finally, a summary of several filter organizations which appear to be well suited to switched-capacitor implementation is presented.
238 citations
TL;DR: A new successive approximation analog-to-digital conversion technique compatible with most MOS process technologies is described, which combines a string of equal value diffused resistors and a binary ratioed capacitor array in a unique circuit configuration so that 12-bit monotonicity is achieved with only 8-bit ratio-accurate circuit elements.
Abstract: A new successive approximation analog-to-digital conversion technique compatible with most MOS process technologies is described. This technique combines a string of equal value diffused resistors and a binary ratioed capacitor array in a unique circuit configuration so that 12-bit monotonicity is achieved with only 8-bit ratio-accurate circuit elements. The comparator is realized by a chopper-stabilized amplifier to reduce the inherently high input offset voltages of MOS amplifiers. Typical performance characteristics taken from a sample of ICs are presented; 12-bit monotonic conversion with differential nonlinearity less than 1/2 LSB is completed in 50 /spl mu/s. The die area, less logic, is 12000 mil/SUP 2/. Because of assured 12-bit monotonicity, this converter should find applications of closed-loop control systems. It seems feasible to extend this technique to 14-bit resolution for use in applications such as digital audio systems.
107 citations
TL;DR: The direct form switched-capacitor offers some useful advantages in comparison to the switched-Capacitor integrator approach, including the rejection of MOS amplifier noise and power supply noise below one-half the sampling rate, less silicon area especially when implementing high Q poles, and potential for multiplexing two or more filters.
Abstract: A new technique enabling the integration of audio frequency filters using standard MOS technology is described. This approach uses ratioed MOS capacitors, MOS amplifiers and switches to realize precision multiplication, summation, and delay functions. With these elements an analog sampled-data direct-form recursive filter, having the general biquadratic transfer function, was integrated in MNOS technology. This filter had a Q=19/spl plusmn/1 without external trimming and it could be electrically programmed into low-pass, bandpass, and high-pass responses. This biquadratic section can be used as a building block for higher order filters. The direct form switched-capacitor offers some useful advantages in comparison to the switched-capacitor integrator approach. These are the rejection of MOS amplifier noise and power supply noise below one-half the sampling rate, less silicon area especially when implementing high Q poles, and potential for multiplexing two or more filters.
75 citations