A 4-Bit Single Chip Analog to Digital Converter with a 1.0 Gigahertz Analog Input Bandwidth

A 4-bit ADC (Analog-to-Digital Converter) has been designed and fabricated on a single Gallium Arsenide chip. This device is believed to be the first single chip implementation of a complete GaAs (Gallium Arsenide) ADC, including S/H (sample-and-hold amplifier), quantizer, clock buffer, and output drivers, reported at this level of performance. The circuit was fabricated with an enhancement-depletion self-aligned gate MESFET (E-D SAGFET) process that in­cludes two layers of metallization and laser trimmable thin-film resistors. Preliminary test results using special high frequency wafer probing techniques have demonstrated a full power analog input bandwidth of 1.0 GHz, and correct operation at low input frequency at a 2.5 GHz sample rate without any laser trimming. Recent acquisition of enhanced high speed logic analyzer equipment is expected to allow high speed SNR testing at multigigahertz sampling rates and high input frequencies.