Abstract: A mixer is presented which utilizes a diode bridge having a first input signal imposed across two opposite nodes of the diode bridge and having a second input signal imposed across the other two nodes of the diode bridge. A set of variable impedance devices are included in the mixer to protect the diodes in the diode bridge from overload conditions. These variable impedance devices can be included in each leg of the diode bridge or can be included in the input leads to the loop. The variable impedance devices control the current through the diodes by having a low impedance under non-overload conditions and having a high impedance under overload conditions. A particularly simple choice of the variable impedance device is a FET which has its gate shorted to its source.