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 was found in a 70s documentation. The transistor is from that time. L1 has 4 turns of...
This circuit triggers a relay when light strikes a sensor. The sensitivity is adjusted in the...
With an output of 7.5 W at 110 V this circuit was found in a 1968 Motorola documentation. The circuit has...