Low frequency noise measurement system using sliding pole for fast settling

摘要

Apparatus and method for performing low-frequency noise measurements on active devices such as operational amplifiers, instrumentation amplifiers and the like. A device under test is settled thermally in a short, controlled interval. The device under test is placed in a test fixture within a closed housing which shields against air flow. A substantial heat sink is urged against the device under test while a pre- heat circuit preheats the device for about 1-2 seconds by forcing it to consume a predetermined amount of energy. The voltage output of the device under test is supplied to a band-pass filter which includes a high- pass filter having a single dominant pole whose frequency may be varied. A control circuit smoothly moves that pole from a first, higher frequency of about 50 Hz to a second, lower frequency of about 0.1 Hz in an interval of only 3 seconds or so, rapidly settling the filter.