Sensitive Phototransistor (CB14653E)

In the figure we show how to polarize a phototransistor to obtain sensitivity. The circuit is from an optoelectronic manual from Texas Instruments.

Field strength meter (CB8220E)
This passive tuned circuit was found in a 90s Popular Electronics. The coils must be according to the...
Digital inverter with transistor (CB25625E)
In the figure we have the simple way to obtain a digital inverter using a general-purpose...
Gain 20 LM386 Amplifier (CB25296E)
This circuit was found in the March 1990 issue of Radio Electronics magazine. The circuit can be...