2 thoughts on “Thermitron (Tube, Valve) Op-Amps”

  1. That’s the first commercial op-amp, it cost about $200 in today’s money. Here’s a nice page about it with a schematic: http://www.allaboutcircuits.com/vol_3/chpt_8/14.html The op-amp is a fine example of how a chip can achieve performance that’s impossible with discrete components. With all the transistors on the same bit of silicon, transistor pairs are naturally matched. Same gain across all variations of temperature, voltage and process. Near-perfect balance in the op=amp’s input differential amplifier. The thing is, nowadays practically everyone considers an op-amp to be a discrete component.

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