An in-probe low-noise low-power variable-gain receive amplifier for medical ultrasound imaging using CMUT transducers

Abstract

In this paper a low-power, low-noise receiver amplifier is designed for interface with capacitive micro-machined ultrasonic transducers (CMUT). In 3D in-probe ultrasound imaging systems, the interface circuit area constraint due to the specified area per CMUT element, and the circuit power constraint for each channel are the main design challenges. A fully-differential variable-gain transimpedance amplifier (VGTIA) is designed for the CMUT signal read-out. Due to the small area and low power consumption, the circuit is suitable for in-probe imaging. The VGTIA is designed for the interface with an ADC block that does the digital conversion inside the probe. The circuit is able to produce a differential output from a Zero-Bias CMUT, where the requirement for an external high voltage dc bias is eliminated. The amplifier is designed and fabricated using a 65 nm CMOS process technology. The measurement results show that the transimpedance amplifier has a gain range of 79---97 dB$$\Omega $$Ω. A noise figure (NF) of 3 dB at a 5 MHz center frequency with an only 180 $$\upmu $$μW power consumption is measured. A total area of 76$$\,\upmu $$μm$$\times $$×50$$\,\upmu $$μm is achieved which relaxes the area requirement for the following ADC block.