Patent ID: 7675353

Claim:
A constant current generator comprising: a bandgap reference circuit for generating differential node voltages; and a single gain stage for amplifying the differential node voltages and generating a constant current, wherein the gain stage includes: a single operational amplifier that receives the differential node voltages on its input terminals; wherein the bandgap reference circuit includes: a first bipolar transistor and a first resistor connected in series between a low voltage source and a first input terminal of the operational amplifier, the first bipolar transistor having a base connected to the low voltage source; a second resistor connected between the low voltage source and the first input terminal of the operational amplifier; a second bipolar transistor connected between the low voltage source and a second input terminal of the operational amplifier, the second bipolar transistor having a base connected to the low voltage source; a third resistor connected between the low voltage source and the second input terminal of the operational amplifier; a first MOS transistor connected between the first input terminal of the operational amplifier and a positive voltage source; and a second MOS transistor connected between the second input terminal of the operational amplifier and the positive voltage source, wherein the gain stage further includes: a third MOS transistor driven by the operational amplifier, the third MOS transistor having a first terminal connected to the low voltage source; a fourth MOS transistor connected between a second terminal of the third MOS transistor and the positive voltage source; and a fifth MOS transistor connected to the positive voltage source, wherein the first, second, fourth, and fifth MOS transistors have gates connected to the second terminal of the third MOS transistor, and wherein the fifth MOS transistor outputs the constant current.