Abstract: A bipolar main transistor Q.sub.1 designed to amplify a high-frequency signal applied to its base, for driving a load connected to its collector lead, has its emitter connected through a low-ohmic feedback resistor R.sub.E to a point of stabilized potential constituted by the emitter of a biasing transistor Q.sub.2 of the same conductivity type (e.g. NPN) as the main transistor, the latter emitter being connected to a terminal of a d-c supply through a much larger resistor R.sub.3 ; the two series-connected resistors R.sub.E, R.sub.3 are capacitively shunted for high frequencies. The biasing transistor Q.sub.2 is driven at a much larger direct current than the main transistor by a control transistor Q.sub.3 traversed by a direct current substantially equaling that of the main transistor Q.sub.1, this control transistor being biased by a voltage divider including a fourth transistor Q.sub.4 connected as a diode and traversed by a current substantially equaling that of the biasing transistor Q.sub.2.