Viewing posts for the category SED

Cascode Enhancement pHEMT Photodiode Preamp

This is pretty small, because it has to be--those are microwave transistors, and will oscillate at the slightest provocation. The axial resistors and TO-92 parts are all for biasing---the actual amplifier is the part between the output coupling cap (the small orange thing in the middle) and the photodiode, which is the white square with the black middle at the right.

Transistor Tester for laser noise canceller

As discussed in medium-gory detail in this paper, these devices can let you do shot-noise limited measurements at baseband with lasers that are as much as 70 dB noisier than that.