Patent ID: 6642778
Filing Date: 2003-11-04
Classification: G05F

Abstract:
A low-voltage reference circuit, comprising:a first current source (I3); a second current source (I4); a third current source (I5); a first bipolar junction transistor (Q3) having an emitter connected to the first current source (I3), and a collector and base connected to VSS; a second bipolar junction transistor (Q4) having an emitter connected to the second current source (I4), and a collector and base connected to VSS; a third bipolar junction transistor (Q5) having a collector, and having an emitter and base connected to VSS; an NMOS transistor (M1) having a drain connected to the third current source (I5), a source, and a gate; a first operational amplifier (A1) having an inverting (âˆ’) input connected to the first current source (I3), a noninverting (+) input connected to the second current source (I4), and an output connected to drive the first, second and third current sources (I3-I5); a second operational amplifier (A4) having a noninverting (+) input, an inverting (âˆ’) input connected to the source of the NMOS transistor (M1) and having an output connected to the gate of the NMOS transistor (M1); a first resistor (R3) having a first terminal connected to the second current source (I4) and having a second terminal connected to the emitter of the second transistor (Q4); a second resistor (R4) having a first terminal connected to the third current source (I5), and having a second terminal connected to the collector of the third transistor (Q5); a third resistor (R8) having a first terminal connected to the third current source (I5), and having a second terminal connected to the noninverting (+) input of the second amplifier (A4); a fourth resistor (R9) having a first terminal connected to the noninverting (+) input of the second amplifier (A4), and having a second terminal connected to VSS; a fifth resistor (R10) having a first terminal connected to the inverting (âˆ’) input of the second amplifier (A4), and having a second terminal connected to VSS.