In the given circuit the input voltage V _ in is shown in figure....

During the positive half cycle of the input waveform, diode ${D}_{1}$ is forward biased and diode ${D}_{2}$ is reverse biased. Here $0 . 6V$ appears across the output as the diode is conducting. During negative half cycle the diode ${D}_{1}$ is reverse biased and ${D}_{2}$ is forward biased, so, $- 0 . 6V$ appears across the output as the diode is conducting in negative direction. This circuit can be used as a voltage limiter. This circuit will not allow any voltage above $0 . 6V$and below $- 0 . 6V$.

Hence, the output waveform is