Abstract: A power amplifier provided with overload protection responsive to the impedance of a load falling below a threshold value having a pair of power output devices connected to the load and driven through a balanced operational amplifier and transistor couplers. The operational amplifier has opposed voltage supply inputs, and each is connected through a first resistor to a voltage source and to the load through a pair of diodes connected in series opposition and a second resistor, and the junction between the diodes is connected to the base of one of the transistor couplers. A fault condition causes current to flow through the diodes lowering the potentials of the voltage supply inputs and the bias on the transistor couplers.