Abstract # 260

L. Y. Nathawad, R. Urata, B. A. Wooley, and D. A. B. Miller, "A 40-GHz-Bandwidth, 4-Bit, Time-Interleaved A/D Converter Using Photoconductive Sampling," IEEE J. Solid-State Circuits 38, 2021 2030 (2003)

GaAs photoconductive switches have been integrated with two parallel 4-bit CMOS analog-to-digital (A/D) converter channels to demonstrate the time-interleaved sampling of wide-band signals. The picosecond sampling aperture provided by the low-temperature-grown-GaAs metal-semiconductor-metal switches, in combination with low-jitter short-pulse lasers, enables the optically-triggered sampling of electrical signals with tens of gigahertz bandwidth at low to medium resolution. A pair of parallel sampling paths, one for sampling and the second for feedthrough cancellation, generate a differential held signal that is quantized by a low-input capacitance, high-speed flash A/D converter. Dynamic offset averaging is employed to improve converter linearity. An experimental time-interleaved tow-channel A/D converter provides about 3.5 effective bits of resolut8ion for inputs up to 40 GHz when tested at an optically-triggered sampling rate of 160 MHz. The sampling rate was limited by the available optical source. Each A/D converter channel operates up to a 640-MHz conversion rate, dissipates 70 mW of power, and occupies an area of 150m x 450m in a 2.5-V, 0.25-m CMOS technology

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