This circuit was found in 80's Popular Electronics. Transistors are commonly used. The potentiometer R5 adjusts the gain.
With the capacitor used, this circuit provides delays of 40 to 60 seconds. Larger capacitors can...
Found in an Electronic Design from the 90's, this circuit generates signals for stepper motor...
The circuit shown in the figure can generate signals up to 1.6 GHz. Coil L1 and capacitor C2 are...