Passive double-balanced mixers comprised of FET quads and diode-rings can work as up- or down-converters in cellular base-station transceivers. High-linearity (IP3), low-noise, and spurious- response up- and down-converters requiring low-level local-oscillator signals have been realized by integrating buffer amplifiers along with the FET or diode mixer cores. Wideband noise in the buffer amplifier stages impairs the received and transmitted signals. This noise can be characterized and specified by a single parameter. By introducing a noise parameter in dBc/Hz for the passive mixer IC, the user can calculate the system-related impairments when using the IC in base-station transmit and receive applications.