An Automatic Data Acquisition System for Semiconductor Device Testing

An automatic data acquisition system was designed and fabricated from both commercially available and proprietary special-purpose equipment to obtain the large quantities of accurate voltage versus current data needed to define and study the voltage-current characteristics of semiconductor devices exposed to neutron bombardment. The operation of the system in tracing out the entire current-voltage characteristic, per preprogrammed instructions, requires only a start command from the operator. The system is capable of measuring currents in the range of 10-10 to 2×10-1 amperes with an absolute accuracy of ±1 percent of reading and a precision (repeatability) of ±0.3 percent of reading, with a maximum voltage drop across the current sampling element of only 5 mV. This low value of voltage drop across the sampling element is made possible by the use of an autoranging technique, which selects discrete values of resistance for sampling the current being measured. The system is capable of programming input voltages from 0 to 50 V in 0.1-mV increments, or input currents from 0 to 2 amperes in increments of 0.01 to 10 μA, depending on current range. The currents are sampled by the current sampler, whose output voltage is amplified by low-noise amplifiers, and measured by a Dymec 2401C-M31 digital voltmeter. The voltmeter readings, along with resistor identification information in digital form from the current sampler, are serialized by a Dymec 2540B coupler and recorded on a Friden Model SFD Flexowriter in both typewritten form and on punched paper tape.