Found in Motorola documentation from the 90's, this circuit has a high input impedance. The power supply must be symmetrical. The circuit can be implemented with modern operational amplifiers.
The circuit shown in the figure can be used to detect the operation of infrared sources whose...
Found in a 90s Hands On Electronics, this small preamp finds applications like microphones and other...
This circuit was found in a 90s Popular Electronics. The frequency is determined by R3 and C1 that...