A bipolar power supply capable of selectably supplying either a positive or a negative voltage at an output terminal. The power supply comprises a first operational amplifier, a second operational amplifier, a first transistor electrically connected to a positive voltage source and a second transistor electrically connected to a negative voltage source. The first transistor is electrically connected to the first operational amplifier and the second transistor is electrically connected to the second operational amplifier so that the first and second amplifiers control the operation of the first and second transistors respectively. The inputs of the first and second operational amplifiers are electrically connected in a manner that prevents them from simultaneously providing large positive voltages at their outputs.