Overload protection for transistor amplifiers - carrier system line amplifiers have separation of frame from cable sheaths

摘要

Cable sheaths, which can be the outer conductors, are separated from the transistor amplifier frame by h.v. capacitors, and amplifier working point stabilisation is achieved by an emitter resistor common to all stages. Input and output terminals and supply connections are protected by Zener diode and voltage arresters. A Zener diode is in parallel with the common emitter resistor. The Zener voltage is a little higher than the stabilisation voltage which drops in normal operation across this resistor. During normal working the stabilising voltage drops across the common emitter resistor. Supply voltage is achieved from the part of the remote d.c. supply lying across the Zener diode and the capacitor switched in parallel.