Simulation modeling of protective circuits of a DC transistor electronic device is considered. It is shown that simulation modeling is one of the advanced research methods. The application of the Simulink program for this purpose is justified. The transistor switching device is considered from the point of view of overvoltages arising when the current is switched off. A simplified circuit of the switching device necessary for conducting research is given. A complete diagram of the Simulink model is given. Protection schemes using resistors, capacitors and varistors are given. The magnitude of overvoltages on a transistor with a different combination of protective circuits is investigated. The dependences of the overvoltage magnitude on the switched current for various combinations of protective circuits are given. The dependences of the overvoltage magnitude on the parameters of the elements of the protective circuits are given. The conclusion about the necessary structure of protective circuits is formulated.