Gain Apparatus for Power Sourcing Equipment of Power Over Ethernet

摘要

A gain circuit for power sourcing equipment of Power over Ethernet is disclosed and provides a guard band for the input offset voltages of its operational amplifier. The guard band may be represented by a voltage value and may be set to be greater than the maximum input offset voltage of the input terminals of the operational amplifier. In some embodiment, the guard band allows the voltage of the negative input terminal of the operational amplifier to be greater than 0 V without sacrificing the gain precision.

主权项

1. A gain circuit for power sourcing equipment adapted to supply power over Ethernet, comprising:
a first resistor and a second resistor; an operational amplifier with a first input terminal, a second input terminal, and an output terminal, whereas (1) the first resistor and the second resistor are connected in series between the output terminal and a ground end, (2) the first input terminal is connected to a voltage output of the power sourcing equipment, and (3) the second input terminal is connected to the output terminal through the second resistor; a switch controller with a clock signal to control whether the second input terminal is connected to the second resistor through a capacitor; and a voltage adjusting circuit adapted to set voltage difference between the first input terminal and the second input terminal to a predetermined value.