Viewing posts for the category SED

Care and Feeding of Tantalum Capacitors

Solid tantalum capacitors have a lot of advantages: very low inductance in surface mount packages, ESR low but not so low that your LDO regulators start oscillating; and good capacitance per unit volume.  Unfortunately they're also prone to burn up when mistreated, which makes many engineers wary of them.  This war story, entitled What a Cap-astrophe! talks about how to treat them properly, and how a bit of TLC after soldering can restore their full performance.

High Dynamic Range FET Bridge Mixers

For RF folks, one of the perennial quests is for better frequency mixers: lower distortion,
lower power, better spurious performance.  FETs can help.  Nowadays CMOS muxes are the devices of choice for HF mixers, but to get the best performance, you still have to know how they work.  Ed Oxner was a long-time Siliconix apps guy, and his paper on High dynamic range FET RF mixers is still right up there with the best: 
(From a Siliconix databook, 1985.)  The FET mux approach is often credited to Dan Tayloe, but since they work just the same, the "Tayloe mixer" should really be called the "Oxner mixer".

Noise Peaks From Linear Voltage Regulators

Erroll Dietz is a remarkable fellow.  He started out at National Semiconductor as Bob Pease's
technician, and rose to become Chief Technology Officer.


Feedback amplifiers generally have an output impedance that rises linearly with frequency---in other words, it's
inductive.  As Dietz's short paper from Electronic Design shows, this effective inductance can
resonate with the output bypass capacitor to cause really nasty noise peaks in the 1-100 kHz region.  If you have an inexplicable noise peak in that range, a small resistor (a few tenths of an ohm to an ohm or two) in series with the regulator output can be just the ticket.

Random resources from my SED posts

Sometimes it's useful to add supporting documents, schematics, scope photos, simulations or other things to Usenet posts.  By popular request I've added links to some of these, in no particular order.

A trick for turning the usual proportional/integral (PI) loop filter of a phaselocked loop (PLL) into a   sweep generator for lock acquisition.

A big slide deck with ideas on Getting Photodetection Right (from a talk given at BBN in Cambridge MA)

A presentation from Texas Instruments showing detailed measurements of the switching noise of their OPA2188 chopper amp.

A paper from LIGO on components with low flicker noise

How To Read SED: Archive Sites and Newsfeeds

One of the nice things about sci.electronics.design is that it's widely redistributed by archive sites, some of which you can also use for posting, which is good since they made such a hash of the new Google Groups one.

Some examples:
electronics-related

Electronics Point

Electron Depot

It's really better to use a proper newsreader such as Thunderbird or Forte Agent.  You can get a free Usenet account from Eternal September.