The Development of the Constant Current Source for a Four-point Probe Instrument

At first, according to the theory of four-point probe, the importance of the constant current source circuit in a four-point probe instrument is demonstrated. The requirements of the constant current source are listed. Then two circuits having been tested by us during our former developing course are elaborated. They are the cascaded mirror-image current source, the voltage-current transforming circuit. Finally, the utilized circuit with a feedback amplifier to output constant current is demonstrated. The graphs of principle, the formulas to calculate the current and the analysis of their performance are all illustrated. At last, the experience of us is summarized.