A broadband downconverter mixer using an operational transconductance amplifier (OTA) in the RF transconductor stage is presented in this paper. By changing the OTA's transconductance through a dc control voltage, the mixer's conversion gain is varied. Experimental results show that the mixer's conversion gain can vary from 17 dB down to 1.2 dB over a 12 GHz bandwidth. The maximum IP1 dB of the mixer is -3.7 dBm and its maximum IIP3 is + 8.6 dBm. Meanwhile, the maximum OP1dB is +7 dBm and the maximum OIP3 is +21 dBm. The circuit consumes a maximum of 5.9 mW of power from a 1.2 V supply. The chip occupies an area of 0.105 mm2 excluding bonding pads.