Viewing posts for the category SED

Temperature Measurement is Hard

Measuring temperature is surprisingly subtle.  There are lots of sensors out there; Digikey sells thermistor sensors interchangeable to +- 0.1 C from several vendors for about $3 in onesies.  IC sensors tout good accuracy and linearity, and come in both analogue and digital versions for way under a buck.  So what's the issue?

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 all the transistors on an array to run at constant 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.