We found this preamplifier with 70 dB gain for microphones in American documentation from the 90's. Consumption is low and equivalent transistors can be used.
This circuit converts a high impedance signal into low impedance. The circuit has unit gain and...
This project came out in an article of mine (Newton C. Braga) in the Popular Electronics magazine of...
This variable oscillator with crystal was found in a Popular Electronics of the 90s. The circuit uses...