Low resistance microcurrent regulated current source

In a regulated current source having an input terminal for connection to a source of energy and an output terminal for delivering a relatively samll, regulated output current to a load:

• a transistor having an input electrode connected to the input terminal, an output electrode connected to the output terminal, and a control electrode for controlling the amount of current delivered by the output electrode to the output terminal;
• first and second non-linear devices adapted for producing dissimilar voltage drops in response to equal currents flowing therethrough;
• differential amplifier means having inputs connected to the non-linear devices and an output connected to the control electrode of the transistor;
• means for applying feedback currents having a predetermined relationship to the load current to the inputs of the amplifier means through the non-linear devices;
• and a resistive element connected electrically in series with the first non-linear device;
• said amplifier means serving to maintain the currents through the non-linear devices substantially equal in magnitude and the voltage differential between the inputs of the amplifier means at a predetermined level, whereby the feedback currents produce dissimilar voltage drops across the non-linear devices and a corresponding voltage drop across the resistive element, the voltage drop across the resistive element and the resistance of said element determining the level of the feedback currents and therefore the level of the load current.