The matching properties of MOS capacitors are modeled and compared with measured data. A weighted-capacitor array design approach is described. Voltage and temperature dependence of MOS capacitors are analyzed, modeled, and compared with measured data. It is shown that to a first-order heavily doped polysilicon accumulates and depletes similar to crystalline silicon.

Matching properties, and voltage and temperature dependence of MOS capacitors

A method for developing a reference voltage in CMOS integrated circuits is described. The circuit uses MOS devices operating in the weak inversion region, as well as a bipolar device formed without process modifications. A brief description of this region of operation is given. Then, the principle of the suggested voltage reference is explained and the final implementation is presented. Higher order effects are discussed, and results from an integrated prototype given.

A CMOS voltage reference

A new CMOS PCM channel filter is described, which includes transmit and receive filters on a single die. This chip displays an idle-channel noise of typically 0 dBrnC0, a power supply rejection ratio of 40-50 dB at 1 kHz, and a fully operational power dissipation of only 35 mW, making it very cost effective in telecommunication switching systems. The design of this chip, including architectural, switched capacitor filter, and amplifier considerations is described, and typical experimental results are presented.

A high performance low power CMOS channel filter

Describes a one-chip PCM codec circuit which has been implemented in the CMOS process. The design uses two separate linear digital-to-analog converters, made with charge redistribution techniques. Experimental results show the circuit to meet accepted requirements and operate with very low power requirements.

Integrated PCM codec

Describes a monolithic NMOS coder/decoder (codec) with associated CCD transversal minimum phase filters which has been successfully implemented. The codec operates by charge redistribution in a binary-weighted capacitor array, with a resistor chain to define individual steps. The experimental performance compares well with PCM codecs implemented with discrete components.

A PCM voice codec with on-chip filters

A staightforward answer to the per-channel CODEC question has been obtained by a CMOS chip pair operating on the capacitive charge redistribution technique. Designed especially for the D4 channel bank, but ideal for various PCM telephone systems and other applications, the compressing A/D converter and expanding D/A converter produce the standard digital approximation to the μ-255 characteristic without the requirement of external components; all analog and digital functions are integrated. The advantages of the per-channel over the shared CODEC are manifest; the configuration separating the two asynchronous conversions maximizes versatility and ease of application.

G. Landsburg

Papers

A two-chip CMOS CODEC