A new 0.25um CMOS on-chip active balun with gain controllability for 5GHz DCR [direct conversion receiver]

An on-chip active balun with good gain and phase mismatch performance of within 0.5 dB and 1 degree, respectively, is presented in this paper. Applicable for direct conversion receiver circuits, the presented balun features reconfigurability in the form of controllable gain, designed to operate in the 5-6 GHz range with a bandwidth of 400 MHz. With good linearity, input/output matching and gain and with improvement in noise performance, the proposed active balun circuit could effectively be used as the first stage of an RF front end replacing the LNA.