METHOD OF PROTECTING FINAL STAGE HIGH OUTPUT TRANSISTOR OF RADIO TRANSMITTER

摘要

PURPOSE:To prevent the deterioration of a high output transistor (TR) due to heat by installing a temperature detection switch element so as to close a circuit when the temperature reaches the setting temperature near the other high output TR used for other controls than APC and ALC so as to control the exciting voltage of the high output TR. CONSTITUTION:The input APC to a control section 5 from a diode D1 detects a DC voltage obtained by a level of a traveling wave at all times, the voltage is used as a control signal to control a PS 1 thereby acting like keeping the output of a PA section constant. Further, the input ALC to the control section 5 from a diode D2 is a DC voltage obtained by a level of a reflected wave, and when the voltage increases abnormally, the voltage of the PS 1 is lowered to protect a TR 3. The temperature detection element 4 is fitted near the TR 3 and the circuit including the temperature detection element 4 is connected to the control section 5 and is turned on at a setting temperature, e.g., 65 deg.C to form a grounding circuit, the control section 5 is operated by the signal to decrease a power voltage PS 1 of a driver 7 or to interrupt the power supply protecting the TR 3 from being left at a high temperature.