MMBT4401 looks like the noise figure might be similar to BC847 if you=20 interpolate the graph up past 100KHz On 1/9/2017 4:46 PM, Van Horn, David wrote: > 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 Noi= se" is kinda meaningless without knowing at what current and over what freq= uencies. > > > > -----Original Message----- > From: speff@interlog.com [mailto:speff@interlog.com] > 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 >> very low noise at or around 457kHz. >> Bonus points if the base resistance and optimal collector current are >> 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 >> up being in the audio region, and behavior at my frequency of interest >> isn't specified. > Ordinary jellybean moderate-power transistors like the 2N4401 are typical= ly 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 ne= ed lower, consider a cascode JFET (or JFET+BJT) configuration and an input = transformer. > > --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 .