BC847 and 850 are proving too high a noise level. I don't see the 4401 in SOT-23 or similar. 1mA would be on the high side for my power budget. I'd love to find a selection guide that gave useful noise data. "Low Noise= " is kinda meaningless without knowing at what current and over what freque= ncies. -----Original Message----- From: speff@interlog.com [mailto:speff@interlog.com]=20 Sent: Monday, January 9, 2017 2:42 PM To: Microcontroller discussion list - Public.; Van Horn, David Subject: Re: [EE] Low noise NPN Quoting "Van Horn, David" : > > Sometimes information seems to be surprisingly hard to come by. > I'm looking for an NPN transistor, preferably in SOT-23, which has=20 > very low noise at or around 457kHz. > Bonus points if the base resistance and optimal collector current are=20 > specified. > My input impedance is low, so FETs are not the optimal choice here. > > I've found tons of "low noise" transistors, but frequently this ends=20 > up being in the audio region, and behavior at my frequency of interest=20 > isn't specified. Ordinary jellybean moderate-power transistors like the 2N4401 are typically= low noise- well under 1nV/sqrt(Hz) typical at 1-10mA Ic,. JFETs like the BF862 are something like 800pV/sqrt(Hz) typical. If you need= lower, consider a cascode JFET (or JFET+BJT) configuration and an input tr= ansformer. --sp --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .