7 Input and Output Connections

The LMH5485-SP-EVM is equipped with SMA connector footprints for easy connection of signal generators and analysis equipment. The EVM can either be for single-ended or differential input or output with 50-Ω termination. For best results, signals must be routed to and from the EVM with cables having 50-Ω characteristic impedance. Either IN+ (J2) or IN– (J1) can be used for single-ended input. The unused connector should be terminated with a 50-Ω resistive SMA load. If no SMA load is available, then the spaces marked C1 or C2 can be loaded with a 0-Ω resistor, and the spaces marked R1 or R4 can be loaded with a 50-Ω to terminate the unused input. Use both IN+ (J2) and IN– (J1) for differential input.

OUT+ (J9) is the output connector for single-ended output signals. The amplifier converts the single-ended or differential input to a differential signal at its output pins. A resistor network (R8, R9, and R10) and transformer on the output of the amplifier (T2) convert the differential output signal to single-ended and provides a 500-Ω load to the amplifier when terminated in 50-Ω. A 50-Ω line-impedance match at OUT+ should be preserved. This results in an output measurement loss, and the overall gain is approximately –20-dB. For more details, see the Applications and Layout Guidelines in the LMH5485-SP Radiation Hardened Assured (RHA) Negative Rail Input, Rail-to-Rail Output, Precision, 850-MHz Fully Differential Amplifier data sheet.