David Gerard Vallancourt

Sampled-current circuits

A method for making practically identical copies of a sampled current without relying on the matching of circuit elements (such as capacitors or transistors) is presented. Compact circuit realizations are discussed, leading to the generation of a family of analog function blocks for the creation, copying, and manipulation of current samples, all free from dependency on element matching. Applications of these circuits include signal processors and A/D (analog-to-digital) and D/A (digital-to-analog) convertors.<<ETX>>

A transistor-only current-mode Sigma Delta modulator

Current-copier circuits are used in the IC realization of a transistor-only second-order Sigma Delta modulator fabricated in a 0.9- mu m digital CMOS process. The 13-bit resolution and 12-bit full-scale linearity make the converter suitable for A/D conversion in high-performance telecommunications applications.<<ETX>>

Noise analysis of current copier circuits

An analysis of the noise characteristics of the most basic current copier cell is presented. Since MOS transistors are used, both thermal and 1/f noise sources occur. Because of sampling, the noise appearing at the output contains both sampled and continuous components. An expression is described for the power spectral density of the output current noise, allowing an assessment of the relative importance of each of the noise sources in a current copier application. A measurement of the noise spectrum of the current copier is shown.<<ETX>>

Analog CMOS filter with full digital programmability

A CMOS analog signal processor using digitally-controlled switch timing rather than capacitor arrays to achieve programmability of both filter topology and transfer functions, will be described. A 5μm CMOS test circuit has demonstrated availability of a dynamic range of 80dB and and ± 3V signal swing at ± 5V power supply.

Yannis Tsividis, Educator

The great universities offer more than a collection of excellent courses and research achievements. A unique culture - a personality - characterizes the institutions that consistently bring out the best in their students and earn their loyalty after graduation. Like-minded faculty and administration can develop this personality in an emergent process, but a consistent, dedicated voice is most effective in shaping it and preserving its fundamental character while letting it evolve with the times and the students. Yannis Tsividis has been that voice in the Department of Electrical Engineering at Columbia University for almost 40 years. Today, the entire Engineering School is enjoying a burst of innovation, with Yannis leading its efforts in education.