a temperature stable bandgap voltage reference source utilizing two substrate bipolar transistors biased at different emitter current densities is provided . switched capacitors are used to input the v be and the δv be of the transistors into an amplifier to provide a reference voltage proportional to the weighted sum of the ptc and ntc voltages . proper selection of the ratio of the switched capacitors renders the reference voltage substantially independent of temperature . in a modified form of the reference , the reference amplifier is implemented by an auto - zeroed operational amplifier which uses switched capacitor techniques and an integrated capacitor to achieve the auto - zeroing function .