A 255 MHz Programmable Gain Amplifier and Low-Pass Filter for Ultra Low Power Impulse-Radio UWB Receivers

A 90 nm-CMOS power-optimized analog baseband chain for ultra-low-power impulse-radio ultra-wideband (IR-UWB) receivers is presented. The proposed device merges the functions of a programmable gain amplifier (PGA) and a low-pass filter (LPF). It consists of the cascade of three biquadratic cells made up by opamps in a series-shunt configuration, which features high input impedance, low load effects in the cascade blocks, and better frequency response. The opamp parameters are included in the overall biquad transfer function. This allows getting very low power performance, since the opamp bandwidth is not required to be much larger than the filter cutoff frequency. Moreover, the current consumption is optimized according to the selected gain level (1.3 mA at 0 dB-gain up to 1.9 mA at 40 dB-gain). The PGA features a 0-40 dB programmable gain range with a 5 dB gain-step. The LPF performs a sixth-order 255 MHz low-pass frequency response. For the overall chain the IIP3 is 14 dBm at 0 dB gain, while the input referred noise is 12.5 nV/root Hz at 40 dB gain.