1 Status operational amplifier OP AMP since its inception in 1963, are developing a very long and linear systems for all parts of the de facto standard. Almost every major line of semiconductor products are the manufacturer of this product operational amplifiers. Depending on the application needs a universal key differentiation, low voltage / low power, high speed type, high precision op amp type four major product categories. Performance levels, amplifier have achieved the following objectives, which in the 20th century, 60 years is unheard of: a bandwidth exceeding 1 GHz; conversion rate of more than 5000 V / s operational At least 10 current voltage, working as little as 0. 9V; input offset voltage below 20 V. 2 Precision amplifier precision amplifier usually refers to less than 1 mV offset voltage op amps, the use of the process, he stressed that the circuit is low noise and low offset performance. With the new sensor technology (such as a missile gyroscope, MEMS MEMS etc.) to promote the use and improvement of performance, the type of accuracy and bandwidth of operational amplifiers are more demand. To meet this demand, the foreign IC launched a number of broadband products. 3 low-noise applications compensate the sensor circuit technology New Precision op amp offering higher requirements on the micro-sensor, because its production is mainly in the low frequency signal and the signal amplitude is low, the resulting imbalance by CMOS technology and low frequency 1 / f noise increased, Micro Sensor Circuit has presented a great challenge. CMOS process to realize the next generation of the same dynamic range, the circuit needs to maintain the momentum greatest possible efficiency and the use of a variety of technologies to reduce the offset voltage and a 1 / f noise . Now the current to reach low-offset, techniques of circuit noise are the following: self-stabilized Z (automatic reset) technology, correlated double sampling (CDS CorrelatedDoubleSampling) technology and chopper stabilized CHS (ChopperStabilization) technology. In this article, AZ and Technology CHS. 3. From a technical zero (AZ) The basic principles is3. 1. From A to Z a zero Technical (AZ) The basic idea is to first sample and record the noise and offset, then its entry or exit of transient signal in addition. Of course, can also be added between the ports of entry and exit to reach an additional noise and zero offset. If the tone does not change with time signals (such as DC disorder), it will be eliminated; If it is a slowly varying low frequency random noise (like a 1 / f noise), will high-pass filter. The principle of Figure 1, assuming that the offset between your reference voltage, enter the reference noise VN. AZ process is divided into two stages: the first step, the signal is isolated, MPA input is shorted, the role of the pulse sampling, the input offset Vos and sampled noise VN and saved, and negative feedback in the form of introduction from port N, the production is controlled by a very small margin, the access of the second phase of the signal, if your hypothesis and VN and sampling the same, then noise and offset will be eliminated. 3. 1. 2 A to Z on the impact of bandwidth bruitbande (1) the impact of noise assumed white noise operational amplifier input white equivalent is equivalent to-3dB FC in the low-pass characteristics (LF) noise, the sampling frequency fs, is usually fc fs>> production from A to Z white noise can be approximated as: