9 V Battery Tester and Cell (CB15087E)

If the battery is good, the LED flashes. This simple tester uses an LM3909 integrated circuit. We found this configuration in an old documentation.

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LC Oscillator Using the 4069 (CIR093E)
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DVM to PC adapter (CB7924E)
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DC Amplifier with Drift Compensation (CB14068E)
of the National Semiconductor of 1994. The same technique can be used with other operators and the...