Abstract—We present the design of Analog front end (AFE) low noise pre-amplifier implemented in a high voltage 0.18-µm CMOS technology for a three dimensional ultrasound bio microscope (3D UBM) application. The fabricated chip has 4X16 pre-amplifiers implemented to interface a 2-D array of high frequency capacitive micro-machined ultrasound transducers (CMUT). Core AFE cell consists of a high-voltage pulser in the transmit path, and a low-noise transimpedance amplifier in the receive path. Proposed system offers a high image resolution by the use of high frequency CMUTs with associated high performance imaging electronics integrated together. Performance requirements and the design methods of the high bandwidth transimpedance amplifier are described in the paper. A single cell of transimpedance (TIA) amplifier and the bias circuit occupies a silicon area of 250X380 µm 2 and the full chip occupies a total silicon area of 10x6.8mm². Keywords—Ultrasound, analog front end, medical imaging, beam forming, biomicroscope, transimpedance gain. I. INTRODUCTION DVANCED imaging equipments used in real time three dimensional body scanning are available as portable or hand held units [1]. Availability of such miniature yet low cost medical imaging systems have created a global trend in shifting the emphasis on personal care from a hospital setting to a primary healthcare professional or to an individual level. This revolutionary change in healthcare has not only improved the personal care management but also helped to shift the emphasis from cure to prevention. In recent times the development in ultrasound imaging is much ahead of its peers largely due to the use of sub-millimeter size capacitive micro machined ultrasound transducers (CMUT) as high frequency acoustic sensors or actuators [2]. Ultrasound medical imaging systems typically find their use in ophthalmology, dermatology and intravascular studies apart from other clinical diagnostic and industrial applications. Three dimensional (3D) Ultrasound Bio microscope (UBM) system provides high image resolution as they use large number of high frequency CMUT elements in 2D array format. In addition to the superior high frequency and larger bandwidth capability of CMUTs, the novel integration methods adopted to interface the CMUT in silicon and the CMOS integrated circuits has further pushed the performance boundaries beyond the large piezoelectric transducer based systems used in the past [2]. However the system design poses challenges in (i) integrating the large number of array Haridas Kuruveettil, Dongning Zhao, Cheng Jia Hao and Minkyu Je are with the Institute of Microelectronics (A-STAR ), 11, Science park road, Science park II, Singapore 117685(e-mail: kuruh@ime.a-star.edu.sg). elements of transducers to interface circuits (ii) designing the multi channel imaging electronics within the power budget and available silicon area as the transducer frequencies are increased to achieve better image resolution. As shown in Fig. 1. Typical transducer interface circuit consists of a high voltage pulser circuit to actuate and a low noise pre amplifier to recover the noisy signal received in the sense mode. A high voltage isolation switch is employed to select either the actuation or sensing mode at a given point in time. Fig. 1 Overall block diagram of the typical ultrasound imaging system including the multi-channel AFE IC, CMUT array, and signal processor In this work, we describe the design, fabrication and measurement of a large bandwidth transimpedance amplifier (TIA) interfacing the high-frequency 2-D CMUT array used for 3-D ultrasound medical imaging applications. Design of TIA is critical to image resolution and receive sensitivity. The IC consists of 4X16 High voltage (HV) pulsers in the transmit path to drive the transducers and 4X16 low-noise TIA with HV protection switches to receive the reflected echo signal. In Section II we briefly explain the AFE system details and the performance requirements. Section III describes the TIA circuit design in detail. Section IV is dedicated to the measurement results and the conclusions are followed in Section V. II. SYSTEM DESCRIPTION A. System Level and Block Level Overview System architecture of a typical high resolution ultrasound imaging system is shown in Fig. 1. A Multi channel planar 2- D transducer array is interfaced to the AFEs by flip chip assembly process [3]-[4]. System architecture of a typical high resolution ultrasound imaging system is shown in Fig. 1. A multi channel planar 2-D array is interfaced to the AFEs by flip chip assembly process. Haridas Kuruveettil, Dongning Zhao, Cheong Jia Hao, and Minkyu Je Analog Front End Low Noise Amplifier in 0.18-µm CMOS for Ultrasound Imaging Applications A World Academy of Science, Engineering and Technology International Journal of Electronics and Communication Engineering Vol:7, No:9, 2013 1168 International Scholarly and Scientific Research & Innovation 7(9) 2013 scholar.waset.org/1307-6892/16654 International Science Index, Electronics and Communication Engineering Vol:7, No:9, 2013 waset.org/Publication/16654