Quoting "Van Horn, David" : > I'm trying to get significantly lower than the 847. > Where did you find a data sheet on this with noise information? =20 > Nothing on ON semi or diodes inc data sheets about noise. It's not on the datasheet. Measurements made by 3rd parties. I have some obsolete TO-92 2SD786 ROHM parts around that are actually specified, IIRC, could send you a couple if it would be helpful. Btw, the discretes behave sensibly above audio but if you decide to try op-amps beware.. the infamous LT1028 belatedly added a chart that showed a huge noise hump at a few hundred kHz. The original datasheet cropped the data to hide the evil behavior, which just happened to be where our signal band is. > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On =20 > Behalf Of William Bross > Sent: Monday, January 9, 2017 3:15 PM > To: Microcontroller discussion list - Public. > Subject: Re: [EE] Low noise NPN > > MMBT4401 looks like the noise figure might be similar to BC847 if =20 > you 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. =20 >> "Low Noise" is kinda meaningless without knowing at what current =20 >> and over what frequencies. >> >> >> >> -----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 =20 >> 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 =20 >> you need lower, consider a cascode JFET (or JFET+BJT) configuration =20 >> and an input transformer. >> >> --sp >> >> > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=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 .