However, because the stability of the emitter potential regulator tube remains unchanged, the emitter voltage decreases, resulting in a decrease in collector current and an increase in collector potential. Because the collector of the amplifier tube is connected with the base of the regulator tube, the base potential increases, resulting in the increase of the collector current and the decrease of the tube voltage drop. Because the amplifier tubes are in series, the output voltage is basically unchanged.
Since the three-terminal voltage regulator can only achieve step-down voltage regulation, the input voltage must be greater than the output voltage, generally higher than the output voltage of about 2v, between 2V-5V is the best effect, the three-terminal voltage regulator, there are two main types, one output voltage is fixed, known as the fixed output three-terminal voltage regulator, the other output voltage is adjustable.