Broadband high-power line driver with synthetic output impedance

Broadband line drivers usually include a back termination resistor at the output to match to the cable they are driving. Half the output power is dissipated in this resistor, therefore halving their efficiency. The resistive termination can be replaced with synthetic impedance using a combination of voltage and current feedback. This implementation is based around a current mirror amplifier capable of producing a 40 V peak-to-peak signal into a 50 Ω load impedance from a ±24 V supply. Using bandwidth enhancement, the small signal bandwidth was 15 MHz and the full power bandwidth was 6 MHz. When driving a 50 m long terminated 50 Ω coaxial cable, the amplifier produced a clean output signal with little ringing, indicating that it is well matched over a broad bandwidth.