Current regulator having start-up circuitry which is turned off after start-up

A current regulator, comprising:

• a base bus;
• an output transistor having a base coupled to the base bus for generating a regulated current;
• a start-up transistor coupled to the base bus which conducts a first current for inducing a start-up current in the base bus;
• a current maintaining transistor coupled to the base bus which conducts a second current for inducing and maintaining an operating current in the base bus in response to the start-up current first being induced in the base bus;
• a first resistor coupled between an emitter of the current maintaining transistor and an emitter of the start-up transistor through which a third current is induced by the second current conducted by the current maintaining transistor;
• and
• a second resistor coupled between the emitter of the start-up transistor and ground through which a fourth current equal to a sum of the first and third currents flows;
• wherein the second current conducted by the current maintaining transistor gradually increases the third current which gradually decreases the first current conducted by the start-up transistor until the start-up transistor turns off.

A method of starting-up a regulator circuit, comprising the steps of:

• establishing a base bus;
• inducing a start-up current in the base bus with a start-up transistor which conducts a first current;
• inducing an operating current in the base bus with a current maintaining transistor which conducts a second current in response to the start-up current first being induced in the base bus;
• establishing a first conduction path between an emitter of the current maintaining transistor and an emitter of the start-up transistor through which a third current is induced by the second current;
• establishing a second conduction path between the emitter of the start-up-transistor and ground through which a fourth current equal to a sum of the first and third currents flows;
• and
• gradually increasing the second current conducted by the current maintaining transistor in order to gradually increase the third current in order to gradually decrease the first current conducted by the start-up transistor in order to turn the start-up transistor off.