A Fast Settling HBT Reference Amplifier for High Speed Digital-to-Analog Converters

Abstract

This paper proposes a fast settling reference amplifier for use with a current-steering Digital-to-Analog Converter (DAC). The reference amplifier utilizes an open loop architecture, resulting in a bandwidth of 2.5 GHz, small chip area and low power. The wide bandwidth of the reference amplifier is shown to be important for fast settling of DAC current output. The reference amplifier is also able to generate a reference current that tracks fast changes of reference voltage, thus is useful in applications such as multiplying DACs and transversal filters. The proposed design was fabricated using a 1 µm GaAs HBT process. The prototype reference amplifier achieves a temperature coefficient of 92 ppm/ • C over a temperature range of 0-100 • C and the reference current changes only ±2.14% when the power supply varies ±0.2 V.