Simple low-noise power supply for electrical transient measurements.
A very simple means is described for rapidly applying and briefly maintaining a large, essentially noiseless, dc voltage across a capacitive load. The technique is suitable for various nonrepetitive electrical transient measurements, such as carrier mobility determination, occurring over timescales ranging from tens of microseconds to several seconds; it essentially eliminates capacitive currents caused by noise in the power supply voltage, which can interfere with measurement of the true transient current. In an example, the noise on a 10-ms transient current (driven by 2000 V dc, and observed as a voltage across a 100-kOmega load resistor) was barely more than the Johnson noise ( approximately 2x10(-11) A rms) to be expected from the resistor.
Vincett
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PS
Xerox Research Centre of Canada, 2480 Dunwin Drive, Mississauga, Ontario, Canada.