Auto-zeroing operational amplifier circuit
 A temperature stable bandgap voltage reference source utilizing bipolar transistors biased at different emitter current densities is provided. Switched capacitors are used to input the V.sub.be and the .DELTA.V.sub.be of the transistors (PTC and NTC voltages, respectively,) into an operational amplifier to provide a reference voltage proportional to the 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. 
Motorola, Inc.
H
H03F
inventional
Stephen H. Richard W. Roger A.
Kelley Ulmer Whatley