CMOS low-power bandwidth-improved derivative superposition mixer using parasitic NPN BJTs

A low-power bandwidth-improved derivative superposition (DS) mixer in a standard 90 nm CMOS technology is analysed in depth. The negative g_m" in saturated NMOS pseudo-differential transistor is compensated by the positive g_m" in the parasitic NPN bipolar junction transistor. Compared with the traditional DS mixer using the dual-NMOS method, the proposed DS mixer shows a wider bandwidth owing to the lower parasitic capacitance at the base. The maximum conversion gain of the DS mixer is 7.2 dB with the 1 dB frequency bandwidth from 0.5 to 6 GHz. Compared with the Gilbert-type mixer, the third-order input interception point (IIP₃) is improved by about 7.5 dB. The DS mixer consumes a DC power of 3.8 mW under 1 V supply.