MEASUREMENT OF COHERENCE FUNCTION BETWEEN NOISE CURRENTS OF TRANSISTORS
Lech Hasse
Abstract:
Relationships between input and output noise parameters of a twoport expressed by correlation and coherence functions has been described. Low noise transimpedance amplifiers (current-to-voltage converters I/V) are used to measure base (gate) and collector (drain) noise currents of transistors in the low frequency range. To reduce an influence of inherent noise of these amplifiers an additional buffer amplifier with special noise properties can be introduce to the input channel of measurement system. A supplementary measurement of the input noise voltage (besides input noise current) can also be used to improve the accuracy of coherence function measurement. To estimate the coherence function with a suitable accuracy adequate digital signal processing procedures should be used.
Keywords:
transistor noise measurement, low noise preamplifiers, coherence function
