Viewing posts from February, 2018

Decap Photo of Terabeam APD Photoreceiver

Decap picture of a Terabeam CD3109 APD/TIA module, taken with a lens glued to a cell
phone camera

Thermal Runaway Found Useful

This odd circuit  is an on-chip temperature balancer that uses thermal runaway to force N transistor arrays to all run at the same temperature.  BJT dissipation goes up at low temperature, with very high gain.  Here's its step response.

Sine Wave Generation with TANH Wave Shaper

Sine wave generation is a perennial problem.

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".