This circuit was found in a 90s Popular Electronics. With it, using a 4066, it is possible to control between 1 to 100 the gain of an operational amplifier like the 741.
In the figure we have an increased dynamic response configuration with the use of a transistor (TR3) in...
This tuned circuit was found in a 1966 Electronic Circuit Handbook. The transistor can be any...
This transmitter for the 40 meter or 7 MHz band was found in a magazine 73 for radio amateurs of...