Infrared detector (CB7814E)

This circuit was found in a Popular Electronics of the 90s. The operational amplifier admits equivalent and the phototransistor can be of any type.

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CMOS Time Base (CB15689E)
This circuit generates 50, 100 and 200 Hz signals from a 3.2768 MHz crystal and has outputs...
Low Pass Filter (CB21764E)
This circuit allows frequencies between 1.8 and 30 MHz to pass. Data for the coils is provided next to...
Automatic Aquarium Heater (CB16857E)
The automatic heating system sensor is a diode placed in a waterproof tube as shown in the figure....