Figure is by the INA105 and so constituted the voltage / current conversion circuit . It can be soldiers 10V control voltage is converted to disability lOµA small current. This circuit is used as a ion chemical reaction of the small current generator. Circuit , using chip a resistor A1 (INA105) and low bias current operational amplifier A2 (OPA124) can conversion accuracy reach 0.1%. output current Lower from the PCB on the leakage current with the required output signal current with the dry sound of the current ratio decision. Access capacitor Cl, can circuit My voice current RMS from about 317nA is reduced to 3.9 nA. Noise current of µA magnitude, flows through Rs and the load the wiring current will lead to considerable error . Load and A2 the input terminal plus guard ring , which can effectively drive the load . Output current increases, to reduce the Rs.