Design And Test Of Sub-pA Class Weak Current Amplifier

With the progress of science and technology and the development of integrated circuit industry,people have put forward higher demands for high-precision amplification and detection technology of weak current.How to effectively amplify and detect weak current has become a subject that cannot be ignored.This paper proposes a method of implementing a sub-p A level weak current amplification and detection circuit.In order to meet the design requirements of the circuit,the following aspects are mainly studied:(1)Design the weak current preamplifier circuit.The pre-amplification circuit design is based on the structure of the charge integrator and incorporates the correlated double sampling technology.In addition,suppress the noise interference in the circuit,and upgrade the operational amplifier structure used in the preamplifier circuit to meet the design requirements of this article.(2)Design to minimize leakage current.In order to meet the circuit's ability to detect sub-p A weak currents,the first thing to consider is to minimize the leakage current in the circuit.Analyze the source,generation mechanism,characteristics and size of the leakage current in the circuit,screen out the key leakage current mechanism that determines the performance of weak current detection,and explore the corresponding solutions.Propose a customized low leakage current switch design and use simulation tools to simulate and verify it.(3)Design low leakage electro-static discharge protection circuit.In order to reduce the interference of electrostatic discharge on the sub-p A weak current detection circuit and maintain the low leakage current level of the circuit,design a fully customized low leakage ESD protection circuit with a diode string structure.The design maintains the low leakage level of the circuit under the premise of completing the electrostatic protection function of the weak current circuit.Use simulation tools to verify the excellent low leakage performance of the structure.Based on SMIC 0.18?m CMOS process,this paper has completed the design,simulation and circuit layout drawing of the weak current preamplifier,low leakage current switch and low leakage current ESD module,and the circuit has been taped out.The circuit test results show that the measurement resolution of the weak current amplifier can reach 0.1 p A,which has fully reached the expected current measurement resolution of ? 0.1 p A.