The DEM-FDA-SOIC-EVM is equipped with SMA input and output connectors for simple interface to signal generators and analysis equipment. To obtain the best results, it is recommended to use 50-Ω characteristic impedance cables between the EVM and lab equipment.

The example schematic in Figure 3-1 shows the EVM configured for a single-ended input with a differential output that is also converted to a single-ended signal through the transformer (T1). This example configuration makes it easy to interface the board with single ended input and output test equipment. In this example case, the input impedance is balanced to accept a connection from a 50-Ω characteristic connection. The resistor R14 is set to 26.1-Ω to provide a balanced impedance that would match the parallel combination formed by the test equipment 50-Ω impedance and resistor R4.

The board can also be configured for differential inputs and differential outputs. Differential inputs can be applied by populating both input SMA connectors (J3 and J5). When using differential inputs, it is important to balance the impedances created by resistors R4 and R14 so that each input is balanced to the same impedance. Otherwise an impedance imbalance will cause output errors. For differential outputs, a shorting resistor should be placed between terminals 1 and 6 and also between terminals 3 and 4 of the transformer (T1) footprint. Both output SMAs should be populated and resistors R8 and R13 removed. It may be necessary to adjust the output loading network formed by R7, R9, and R11 if a differential output impedance match other than 50-Ω is required.

Additional features of the board include optional AC coupling at the inputs and outputs of the amplifier circuit. The input side traces include series 0603 resistor pads prior to the input termination resistors, denoted as R16 and R17, to provide optional AC coupling. The pads of transformer T1 have been extended inward to enable AC coupling at the output of the device. If the board is to be used with DC coupling, the transformer pad extensions can be left unconnected and R16 and R17 should be populated with 0-Ω resistors.