An RF peak-detector circuit can operate over a wide range and can compensate or correct an output voltage error term that depends on the thermal voltage and the input signal voltage. At or near a minimum value of the input signal voltage range, such compensation can include a scaled base-emitter ratioing of bipolar junction transistors used to generate the output voltage, each of which can be biased by a primary current. At or near a maximum value of the input signal voltage range, this can include using an auxiliary bias current circuit that can shift auxiliary bias current between these bipolar junction transistors. The auxiliary bias current circuit can include scaled bipolar junction transistors in a cross-coupled configuration and an equivalent resistance circuit between emitters of the cross-coupled BJTs. This can provide a robust approach for improving the accuracy of an RF peak-detector circuit over a wide range.