AN-72: The aegis of this blog.
This month of September 2022 marks 50 years after the introduction of the LM3900 by National Semiconductor. The LM3900 was intended to support the vast majority of the standard op amp application designs, in lower cost single power supply control systems.
It's a brillant chip design, using novel current mode inputs. I was late comer to a local Silicon Valley gathering called Analog Afficionados. Had I atteneded just a few years earlier, I might have met in person the National Semiconductor luminaries behind the LM3900 such as Tom Frederiksen.
It's a brillant chip design, using novel current mode inputs. I was late comer to a local Silicon Valley gathering called Analog Afficionados. Had I atteneded just a few years earlier, I might have met in person the National Semiconductor luminaries behind the LM3900 such as Tom Frederiksen.
This op amp profoundly affected my life. Before I even understood "conventional" op amps, I first discovered the LM3900 as a teenager. This was in 1974, when I was able to get a few devices, buying them from a Radio Shack store in Portland, Oregon.
For music synthesizer applications, among the first circuits I ever built was the LM3900 VCO, straight out of AN-72. It was one of the easiest forms of access to a VCO. Of course, I quickly learned of it's limitations as well. But: that a very cheap device could do so many different things, including a relatively simple VCO, was absolutely amazing.
For music synthesizer applications, among the first circuits I ever built was the LM3900 VCO, straight out of AN-72. It was one of the easiest forms of access to a VCO. Of course, I quickly learned of it's limitations as well. But: that a very cheap device could do so many different things, including a relatively simple VCO, was absolutely amazing.
In the 1970s, synthesizer pioneers like Serge Tcherepnin found novel uses for the LM3900 for modular synthesizers, including a VCO which derives it's volt/octave exponential response directly from the LM3900. He also created a novel waveshaper, based on the LM3900.
Happy Birthday LM3900!
Happy Birthday LM3900!
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