This circuit was found in a Popular Electronics from the 90s. The transistors are general purpose, and the gain depends on the ratio between R2 and R1.
We found this circuit in the La Radio per Tutti magazine in Italy in 1926. The coil can be made...
This circuit was found in the March 1999 issue of Electronics Now magazine. The meter is analog and...
The basis of this circuit is the 723 integrated circuit, not very common today. We obtained this...