A buffer amplifier is designed to follow low level stages, e.g. an oscillator, mixer, modulator or demodulator. To perform well, these active components cannot be under loaded. That is, it needs buffering. The buffer amplifiers raise the power level of the signal and also isolate the local oscillator. NXP parts that can be used as a buffer are shown on the upper right hand side. A mixer is nonlinear active element, designed to generate harmonics which we use to up or down convert signals with a particular frequency. The BGA2022, shown on the lower right hand side, is a linear mixer that is suitable for CDMA/TDMA applications. It consumes low current and offers high isolation.