Process/Temperature Variation Tolerant Precision Signal Strength Indicator

A receiving signal strength indicator (RSSI) built with transconductance amplifiers is presented. The RSSI achieves high tolerance to process/temperature variations by utilizing the unique nature of branch currents in a transconductance amplifier. These branch currents are used to implement a current-mode rectifier and amplitude clipping circuit that are tolerant of process variations. An on-chip offset control loop permits the entire RSSI to be realized with only one external component. In 0.18-mum CMOS with a 1.8 V supply, the RSSI draws 2.5 mA and provides 80 dB of offset suppression and more than 75 dB of log-linear range with less than +/ - 2-dB error due to process variation.