GaAs/GaAlAs high electron mobility transistors for analog-to-digital converter applications

The use of GaAs/GaAlAs high electron mobility transistors (HEMTs) for analog-to-digital converter applications has been studied. HEMTs have shown superior device stability and uniformity to those of GaAs MESFETs. Because of the buried channel conduction and the control of MBE layers, HEMTs are suitable for high speed and high resolution ADCs. 5-bit ADCs, 5-bit DACs, and timing and control circuits, all built with HEMTs, have been demonstrated. A waveform reconstruction using these three chips has been performed at 140 Mega samples per second with 4-bit accuracy.