Who we are
ZeptoBars is a Russian based R&D company focused on microelectronics and high-tech.
We are working on our commercial, slightly unusual microelectronic product and on the weekends having fun dissolving microchips in boiling acid. We are also trying to reinvent dye lasers utilizing the most recent advances in micro- and optoelectronics.
Datasheet mentions "laser trimming" but we see voltage set via mask and 2 fuses for fine tuning. It is possible though that they have common values set in mask (like this 3.3V one) , and rare voltages laser trimmed.
Die size 500x356 µm, 500nm technology.
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Die size 976x770 µm.
Quartz crystal is mounted on springs - in order to reduce impact of vibration on oscillation stability and to make it's damage less likely:
There is an oscillator IC soldered on the ceramic PCB, as well as 0.01uF power supply decoupling cap. It seems we need to go deeper:
Die size 1194x897 µm, 800nm technology.
Die size 343x343 µm. Comparing to NXP BC847B die area is 1.5x larger (0.118 vs 0.076mm²), but maximum continuous collector current is 6 times higher (600mA vs 100mA, SOT-23 in both cases). This huge increase in current per transistor area is achieved by shunting thin (=high-resistance) base layer with metal. High resistance of base layer is the limiting factor for maximum collector current in BC847B.