Research On Measurement Of Micro Current

With the development of science, the technique of micro current measurement and detect is indispensable. Micro current measurement technique is used in many fields and its development plays an important role in relate fields.Circuit for pA measurement was designed by analysis in micro current measurement method in this paper. By being analyzed two ordinary ways which are high input impedance method and integration method, swithched capacitor for micro current measurement method is advanced first in this field. With this method Current is changed to Voltage , then DC(direct current) is modulated AC (Alternating Current) and amplified, and the value of AC is in direct proportion to the value of measured Circuit. This new method is easier to adjust than high input impedance and respond shorter than integration method.The most important technique is voltage amplifier design in study of micro current measurement on condition that noise is restrained. Select frequency amplifier is presented in this paper which amplify the signal from integration circuit, then the signal from select frequency amplifier is demodulated by switched phase detector. Select frequency amplifier in this paper constitute LPF(Low-Pass Filter) and HPF(High-Pass Filter). It is easy to adjust and to design because there is less parameter. Its enlargement factor arrives to 160,000 because it restrains noise effectively.The whole circuit system has many characters such as small excursion, good linear ratio, stability etc.