AUTOMATED-SYSTEM FOR EQUIVALENT NOISE CHARGE MEASUREMENTS FROM 10 NS TO 10 MU-S

Noise measurements versus filter time constant constitute a very powerful method to investigate series, parallel and 1/f noise contributions in front end electronics. Usually performed with a set of filters and a multichannel analyser, they are tedious and often limited to values greater than 100 ns. We describe here a very low noise bipolar filter whose time constant can be selected via GPIB bus from 10ns to 10 mus in 10 steps. The data are transferred from a digital scope to a computer which generates a baseline histogram and determines the overall gain. The ENC is then calculated for each time constant and a fit to the results determines the various noise parameters.