A Class AB Programmable Gain Amplifier for an UWB Breast Cancer Detection System

This paper presents the design of a programmable gain amplifier (PGA) to be used in a ultra-wide band (UWB) breast cancer detection receiver. The circuit architecture compromises an input fully differential difference amplifier (FDDA) with folded cascode and floating current class AB output in an adjustable voltage feedback loop. Furthermore, different compensation capacitors were used to enhance its bandwidth according to the gain configuration. It has four different voltage gain values (V/V) of 5.5, 8.25, 16.5 and 33, using independent common mode voltages at the input and output. The circuit was taped-out in the TSMC 180nm technology and the measured results are reported. The circuit achieved adequate specifications for the system, such as 7.1MHz of 3-dB bandwidth for its highest gain, slew-rate surpassing 35 V/mu s, THD better than -54 dBc and a very small active area of only 0.079mm(2).