Hi Chris,
my pleasure. I prefer the matching fixed without a trim pot. Also, I generally avoid touching the DUT's with my fingers prior to test as the slight warming introduces a measurement and matching uncertainty. Unless one is after only one matched pair, I am not sure if a sample size of 2N5551= 20 ea. and 2N5401 = 20 ea. is sufficient. I found the 2N5551 and 2N5401 I have here with a very wide beta distribution. I am estimating one needs about 50 ea. to find a few good matching pairs.
my pleasure. I prefer the matching fixed without a trim pot. Also, I generally avoid touching the DUT's with my fingers prior to test as the slight warming introduces a measurement and matching uncertainty. Unless one is after only one matched pair, I am not sure if a sample size of 2N5551= 20 ea. and 2N5401 = 20 ea. is sufficient. I found the 2N5551 and 2N5401 I have here with a very wide beta distribution. I am estimating one needs about 50 ea. to find a few good matching pairs.