Patent ID: 7990130

Claim:
A band gap reference voltage circuit for supplying a reference voltage constant with temperature, comprising: a first power source configured to generate a first voltage; a second power source powered by the first voltage to generate a second voltage independent of fluctuations of the first voltage from the first power source; a first temperature sensor having a first temperature characteristic; a second temperature sensor having a second temperature characteristic; a first current mirror circuit powered by the second voltage to drive the first temperature sensor to generate a first sensor voltage across the first temperature sensor and caused by the first sensor voltage to flow a first sensor current through the first current mirror circuit; a second current mirror circuit powered by the second voltage to drive the second temperature sensor via a resistor to generate a second sensor voltage across the second temperature sensor and caused by a sum of the second sensor voltage and a voltage appearing across the resistor to flow a second sensor current having a temperature dependency polarity through the second current mirror circuit; a current coupler configured to use one of the first and second sensor currents as a reference current to generate the reference voltage having the same temperature dependency polarity as the reference current; and a polarity offset circuit configured to provide the reference voltage with the opposite temperature dependency polarity to make the voltage reference substantially independent of temperature, wherein the second power source is responsive to a difference between the first sensor current and the second sensor current to change the second voltage such that the first and second sensor currents become substantially equal, and wherein when the first and second sensor currents are substantially equal, the resistor produces thereacross a voltage substantially equal to a difference between the first and second sensor voltage and having a temperature dependency polarity determined by the first and second temperature characteristics of the first and second temperature sensors, which polarity determines the temperature dependency polarity of the reference current.