This circuit was taken from Maxim documentation from the 1990s. It can be implemented on the basis of modern operational amplifiers. Power supply doesn't have to be symmetrical.
This circuit is from a 1997 publication, but it can be assembled with a BD136 for TR1. The...
This long-time circuit uses a field effect transistor, which may be the BF245, and depends on a...
We found this transmitter in a Popular Electronics from 1992. The circuit transmits in the range of...