Logarithmic programmable preamplifier dedicated to ultrasonic receivers

This paper concerns the design, the implementation and the validation of a fully integrated preamplifier dedicated to ultrasonic receivers. The preamplification technique is based on two amplification stages: a logarithmic stage called True Logarithmic Amplifier (TLA) and a programmable-gain module built around a Timing Gain Compensator (TGC). The TLA largely amplifies small amplitude signals, and moderately the large amplitude ones. However, the TGC is used to compensate signal attenuation caused by its traveling several human body tissues. Those main building blocks of an ultrasonic receiver are realized using CMOS 0.35 /spl mu/m technology. Spectre simulations of both the TLA and TGC show unity gain bandwidths of 100 MHz and 127 MHz respectively when driving a load of 1 pF. Measurements of the fabricated chip are done in our laboratory using an external digital controller programmed in FPGA. The total chip area is 7.2 mm/sup 2/ including the digital part needed to program the TGC.