Curvature compensated band-gap design

A circuit for providing a reference voltage, comprising:

• a first diode connected between a proportional to absolute temperature current source and ground;
• a first resistance connected between the first diode and the proportional to absolute temperature current source;
• a first opamp having a first input connected to a node between the first resistance and the first diode, an output connected to the gate of a first transistor connected between a high voltage level and ground, wherein the first transistor is connected to ground though a second resistance and the second input of the first opamp is connect to a node between the first transistor and the second resistance;
• a second diode connected between ground and the high voltage level, wherein the second diode is connected to the voltage level by a first and a second leg, wherein:
• the first leg includes a second transistor whose gate is connected to receive the output of the first opamp;
• and
• the second leg includes a third transistor connected in series with a resistive voltage divider, where the resistive voltage divider is connected between the second diode and the third transistor;
• and
• a second opamp having an output connected to the gate of the third transistor, a first input connected to a node between the proportional to absolute temperature current source and the first resistance, and a second input connected to a node of the resistive voltage divider,
• wherein the reference voltage is provided from a node between the third transistor and the resistive voltage divider.