Overload protection circuit for push=pull HF power output stages - measures reflection factor, asymmetry and output transistor currents to control input gain and balance

摘要

The circuit protects transistors in h.f. power output stages from overloading. Circuits measure the reflection factor, the asymmetry, the currents through the transistors of the pushbull output stages and the drve level of the driving stage. All these variables are brought to the same level corresponding to normal generation and applied via diodes to the input of a comparator. The comparator controls input gain to prevent overloading.