Bias Tee - Application

Application

A bias tee is used to insert DC power into an AC signal to power remote antenna amplifiers or other devices. It is usually positioned at the receiving end of the coaxial cable to pass DC power from an external source to the coaxial cable running to powered device. A bias “T” consists of a feed inductor to deliver DC to a connector on the device side and a blocking capacitor to keep DC from passing through to the receiver. The RF signal is connected directly from one connector to the other with only the blocking capacitor in series. The internal blocking diode prevents damage to the bias “T” if reverse supply voltage is applied.

Biasing for photodiodes (vacuum and solid state), Microchannel plate detectors, transistors, and triodes. High frequencies are not leaking into a common power supply rail and noise from the power supply does not appear on the signal line. Bias "T" has been used in a variety of applications, but is generally used to provide an RF signal and power to a remote device where running two separate cables would not be advantageous. Examples of this are: Power over Ethernet, active antennas, low-noise amplifiers, and down converters