Patent ID: 9706610
Date: 2017-07-11
CPC Classifications: H05B,Y02B

Claim:
1. A circuit for driving a string of light emitting diodes, the circuit comprising: a first transistor having a gate, a source coupled to ground through a first resistive element, and a drain; a second transistor having a gate, a source electrically coupled to ground, and a drain for electrical connection to the string of light emitting diodes; circuitry operable to provide a regulated voltage to the source of the first transistor, the circuitry comprising an operational amplifier including an inverting input electrically coupled to the source of the first transistor, and an output electrically coupled to the gate of the first transistor; a second resistive element having a first end coupled electrically to a gate of the first transistor and a second end coupled electrically to the gate of the second transistor; a first current source coupled electrically between the second end of the second resistive element and ground; and a third resistive element having one end coupled electrically to the drain of the first transistor and a second end coupled electrically to the drain of the second transistor.