What is the form of connection for RJ45 connectors?

In an Ethernet device, a network transformer is added to the base whenever the RJ45 belt transformer is connected by PHY. Some transformer base tap power supply, and some capacitance to ground. And when the power supply, the power value can be different, 3.3 V, 2.5 V, 1.8 V have. What is the function of this transformer after all?

Here is a rough answer: 1, why some base tap connected to the power supply? A little grounded? This is the first choice with the use of PHY chip UTP driver type of choice, this type of driver has two types, voltage-driven and current-driven. Voltage-driven will be connected to the power supply; current-driven can be directly connected to a capacitor to the ground! So for different chips, Base Tap Connection, and PHY is closely related, specific also have to see the chip datasheet and see the planning. 2. Why do you connect the power to a different voltage? This is also the choice of regular UTP port levels in the PHY chip data used. The choice of what level, must be connected to the corresponding voltage. If it's 2.5 V, pull it up to 2.5 V, if it's 3.3 V, pull it up to 3.3 V. RJ45 network connector 3, what is the role of this transformer after all, can not be connected it. In theory, it can be directly connected to RJ45 without the need for a transformer, is also able to work properly. However, the transmission distance is very limited, and when received at a different level network port, there will be an impact. And there is a lot of external annoyance to the chip. When connected to the network transformer, it is primarily used for signal level coupling. First, it enhances the signal and makes it travel farther; second, it insulates the chip end from the outside world, making it more resistant to interference and providing greater protection to the chip (such as lightning strikes) ; and third, when receiving different levels (such as some PHY chip is 2.5 V, some PHY chip is 3.3 V) of the network interface, will not affect each other devices. RJ45 adapter. Generally speaking, network transformer has the functions of signal transmission, impedance matching, waveform correction, signal clutter suppression and high voltage isolation.