Archive for May, 2017


May 14, 2017

Now I am done for the time being with analyzing the ultra low noise Zener diode 2DW23x, including building low noise measurement amplifiers. Some summaries can be found here and here. What remains are long-term burn-in and stability tests which run 24/7 for about half a year.

The motivation was to develop a digitally controlled ultra-low noise laser diode drivers for holography applications. This is a long-term project too. In the meanwhile, some first development prototypes were made, and eben without too much effort they sport already very low noise. The only noteworthy thing is that there was at first a considerable feed-through via the DAC from the I2C digital bus. This was completely eliminated by using an opto-coupler – not just for galvanically isolating the bus but rather for interrupting any communication to the DAC except for a brief moment when the output current needs to be changed.

Here a picture of the current test setup, soon it is time to draft a first PCB version:
LD proto

In the middle there is an Arduino Nano, plus DAC/ADCs for digita/analog interfacing via I2C bus. To the left a low power (1.5A) PWM TEC controller for testing. On the right I used a left-over PCB from my old analog TEC/laser diode driver, for the actual analog current output driver including precision, bulk metal foil current sense resistors.