Wide-Range Low Current Measurements of Diode Reverse Currents with Automatic Ranging Features

This paper describes a method used successfully by the author in measuring silicon diode reverse leakage currents. The technique used is straightforward and provides wide-range, low current measurements with improved accuracies and automatic ranging features. The full-scale indications extend from 10-3 through 10-10 amperes in eight decade ranges. The full-scale accuracies achieved are better than ±0.5 per cent on ranges 10-3 through 10-8 amperes, ±1 per cent on the 10-9 ampere range, and ±10 per cent on the 10-10 ampere range. The automatic ranging feature exhibits a response of 10 msec per range. The method used is based on sensing the voltage drop (ES) across a sensing resistor (RS). This sensing resistor is in series with the reverse biased diode, as shown in Fig. 1. The sensing voltage is then amplified to an appropriate level (Eo) which can be more easily and accurately measured and/or digitized, depending upon the type of output display and storage method used.