The output won't be zero. It will more or less track the input voltage minus 3 diode drops (nominally 0.7 V), that is, it will be about 2.1 volts lower than the input voltage. So if there is 3 volts at the input, the output will be around one volt.
The output won't be zero. It will more or less track the input voltage minus 3 diode drops (nominally 0.7 V), that is, it will be about 2.1 volts lower than the input voltage. So if there is 3 volts at the input, the output will be around one volt.