Differential Amplifier

The founder of this LLC started a hobby to collect analog oscilloscope in late 2016. The new well paid software engineering job in Silicon Valley provided the initial capital required to fulfill this hobby. 

Within this hobby, the most beautiful piece is the Tektronix 7A13 Differential Comparator. It was a weird name and no one should what it means after seeing the name for the first time. After all, comparator is an analog circuit that output a digital value, what does it have anything to do with analog oscilloscope.

Well, the differential comparator is a poor name. What it really means is differential amplifier with comparison voltage source. The comparison voltage source is a optional input signal source that is built into the differential amplifier to shift the signal trace with precision DC voltage. So the people back in analog oscilloscope days and super zoom in on a trace to measure tiny variation. 

Back in the analog days, whenever the signal trace goes off screen bad things happens, non-existing signals were added to the trace on the screen. This caused big problem to super zoom in on the trace. The differential comparator come to the rescue. 

The differential amplifier/comparators were designed in such way that they add very minimum distortion when the signal goes off screen. The datasheet in 7A13 claims a virtual 25600 div screen height. 

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After decades of production the very last off-the-shelf differential amplifier ceased production in late 2010s by LeCroy (formerly Preamble). Thus, it give the founder of this LLC a opportunity to pursuit his dream to produce one by himself as a off-the-shelf commercial product. A few trial units were attempted, nothing fancy, until the recent development of our JFET input 1nV/rtHz Differential Amplifier with Comparison and Variable Bandwidth. 

  1. 3nV/rtHz 10MHz JFET input Differential Amplifier with ADA4625 in an instrumentation amplifier configuration with variable bandwidth
  2. 1nV/rtHz 200MHz BJT input Differential Amplifier with LTC6228 in an instrumentation amplifier configuration
  3. 1nV/rtHz 100MHz JFET input Differential Amplifier