Static relay and application thereof to a bipolar inverter or to a load in which a current flows in a random direction

A relay authorizing or stopping the flow of a current in a using circuit comprising a power stage having at least one bipolar power transistor of a first type, whose emitter is connected to a first terminal of the using circuit and whose collector is connected by a low value impedance to a second terminal of the using circuit, and an amplifier stage for controlling the power transistor for authorizing or interrupting the flow of current in the using circuit, said amplifier stage including:

• at least one bipolar control transistor of a second type opposite to the first type and wherein one of said at least one bipolar control transistor of the second type has its emitter connected to the second terminal of the using circuit and its collector connected to the base of the power transistor,
• a high value resistor connecting the base and emitter of the power stage transistor, the value of this high value resistor being selected in order to maintain at a constant value the base-emitter voltage of the power transistor when the transistor of the amplifier stage is in the off state, so that a supply of power to the amplifier stage is constituted by the connection of the amplifier stage to the first and second terminals of the using circuit, the base of the control transistor receiving a control current determining the intensity of the current circulating in the using circuit, the impedance of the power stage varying in the reverse direction to the value of the control current, the low value impedance being chosen so that the collector-base junction of the power transistor is polarized in the forward direction, at saturation.