A transimpedance amplifier for capacitive micromachined ultrasonic transducers

Abstract

In this thesis a design of a CMOS transimpedance amplifier (TIA) for a capacitive micro-machined ultrasonic transducer (CMUT) is presented. CMUT’s have a high electrical impedance when used as receivers. Any capacitance between the CMUT and a high impedance amplifier will degrade the frequency response. So, we need to amplify the current rather than the voltage. This approach requires a transimpedance amplifier. The designed TIA has a 30 MHz bandwidth and 400 kΩ transimpedance gain. The total input referred current noise of the TIA is 270 fA/√Hz at 10 MHz. The noise figure of the TIA is 2.7 dB at 10 MHz when connected to the CMUT with 200 kΩ source resistance. The power consumption of the TIA is 10.5 mW and the size of the TIA layout is 133µm x 45µm. The TIA chip will be fabricated in AMS C35B4C3 (0.35µm) process.