Si Monolithic High-precision Low Offset Op Amp Developed

Described is an operational amplifier configuration implemented as a true high precision low offset amplifier in this thesis. It enables the dc open loop gain and The CMMR high to 125dB and 120dB, respectively. The offset voltage is also low to 270μv ,with the bias current of 2.5nA.These indexes are higher than those of general amplifiers by almost an order of magnitude. Why is these characteristics achieved? The reason is that firstly, input stage adopts two key techniques: Bias-Current -Cancellation Technique, Offset Trimming Techniques. The purpose of which is to decrease bias current and offset voltage respectively. Secondly, In the layout design, common centroid geometry is introduced in input differential pair. in order to alleviate the effects of thermal feedback, input stage is placed where it is far away from thermal output stage. This circuit is simulated with HSPICE .And the device is fabricated using a standard 2μm bipolar process in sichuan institute of solid-state circuits. Then wafers are tested on probe station to detect if which can operate. In the end the performance measurement of the products having been packaged is accomplished with a op amp test instrument. The result of test accords with the expected desire.