A negative overvoltage protection circuit for stages having a transistor with collector output and with the emitter connected to a reference voltage line; a diode (D1) for protection against negative overvoltages present on the output (Vout) is arranged between the collector and the output of the stage. In order to give the output of the stage a presettable minimum voltage level, the reference voltage line is set to a preset voltage which differs from the ground voltage. For this purpose, the circuit comprises an operational amplifier (Op) in a voltage-follower configuration, the output whereof is connected to the reference voltage line, a diode (D2) which is connected between the ground and the non-inverting terminal of the operational amplifier (Op), and a current source which is connected between the non-inverting input of the operational amplifier (Op) and a negative supply line (-VEE).