Abstract: A non-linear active device (32), such as a FET, multiplies multiplicand signals to generate a product signal. A combining circuit (24) combines multiplicand signals into a combined signal. An input matching and conditioning network (28) couples the combined signal to an input of the active device (32). This network (28) matches impedances between sources for the multiplicand signals and the active device (32) at the frequencies of the multiplicand signals, and desirably shorts the product signal's frequencies. A feedback resistor (36) couples between the output and input of the active device (32) to lower impedance at the output and to stabilize the active device (32). An output matching and conditioning network (40) couples a mixed signal from the output of the active device to an output circuit (42). This network (40) matches impedances between the output circuit (42) and the active device (32) at the frequencies of the product signal, and desirably shorts the multiplicand signals' frequencies.