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.
This modulated light transmitter was found in a 90s Popular Electronics. In place of the lamp with...
On this website we show how to calculate the components of this circuit for other frequencies. The basic...
This circuit using only transistors was found in documentation from 1977. The frequency is 4250...