Am 01.09.2016 um 16:36 schrieb jimlux: > On 8/31/16 10:24 PM, Gerhard Hoffmann wrote: >> Am 01.09.2016 um 06:07 schrieb Bruce Griffiths: >>> I have a quad LT3042 PCB that I must get around to assembling.One >>> potential issue with the LT3042 is the relatively high noise at low >>> frequencies when the capacititve bypassing of the resistor that sets >>> the output voltage is ineffective. >> >> I wonder where that relatively high noise on the LT3042 might hide. >> >> < >> https://www.flickr.com/photos/137684711@N07/24070698809/in/datetaken/lightbox/ >> >>> >> > > what's the input source for these measurements? Batteries? > Either NiMH batteries or a R&S NGT20 with the post filter box as in page 9 of < http://www.hoffmann-hochfrequenz.de/downloads/Noise_Measurements_On_Some_Laboratory_Power_Supplies.pdf > That would not make much of a difference. Prefilter/test box and preamp were isolated and in an another large ALU cargo box with beryllium copper finger stock on the door and BNC bulkhead feedthroughs. The preamp runs on NiMH batteries. It's input connection is just one semirigid SMA cable. If the testbox & preamp box touch, the resulting loop creates an explosion of interference. I used "The Art Of Electronics V3" and Aldert van der Ziel's "Noise in Solid State Devices And Circuits" as insulators. A good foundation to build upon, in every respect. :-) regards, Gerhard

Am 01.09.2016 um 06:56 schrieb Gerhard Hoffmann: > Am 01.09.2016 um 05:35 schrieb Charles Steinmetz: >> >> The suggestion to use LT3042s is a good one, but note that it has an >> output current rating of 200mA. The Tbolt needs ~250mA at +5v, and >> ~700mA at +12v [at startup -- but only ~150mA steady-state, depending >> on ambient temperature]. LT3042s can be used in parallel, so two of >> them for the +5v supply and four of them for the +12v supply would be >> required. That isn't so bad for the +5v supply, but seems excessive >> for the +12v supply (particularly when three of the four are needed >> only during warmup from cold). >> > I have made a stamp-sized layout for LT3042 + external npn power > transistor > as shown in the data sheet. > Not fabricated, let alone tested. update: fabricated on a rainy Sunday and initially tested. Output voltage is 5 Volts. < https://www.flickr.com/photos/137684711@N07/29197476530/in/dateposted-public/ > The preliminary noise spectrum is < https://www.flickr.com/photos/137684711@N07/29452163806/in/dateposted-public/> without appropriate shielding, powered from R&S NGT20 @ 8V. The faster than 1/f noise rise is caused by the pre-amplifier. Still quite OK. regards, Gerhard