While operating as split supply, apply positive supply voltage to VCC+, negative supply to VCC-, and ground reference from supply to GND. The board can also be configured for single supply operation by connecting the positive supply voltage to VCC+ and ground to GND and VCC-.

The DEM-FDA-DGK-EVM is equipped with SMA input and output connectors for simple interface to signal generators and analysis equipment. To obtain the best results, use of 50-Ω characteristic impedance cables is recommended 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 R9 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 R9 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 R11 and R15 removed. It may be necessary to adjust the output loading network formed by R8, R12, and R14 if a differential output impedance match other than 50-Ω is required.

FDAs have a feature to externally drive output common mode (Vocm). This feature can be utilized by populating equivalent value resistors for R1 and R2 to VCC+ and VCC-. This sets the output common mode to mid-supply, a common configuration. Additionally, the option to drive Vocm with the SMA connector exists. For this use case, do not populate R1 or R2. If there is need to terminate the Vocm signal source into 50-Ω, C3 can be replaced by a 50-Ω resistor.

Many TI op-amps have a shutdown or power down (PD) feature; this allows for the amplifier to appear as a high impedance load and enables low current draw. This feature is often active low and can be left floating or be driven to a value. In the case of the THS4130 shown in the schematic, driving the PD pin to VCC- will place the amplifier in power down. For convenience and ease of use, the EVM contains a header and jumper to control PD functionality without externally driving the PD pin. If an external signal is needed to drive PD, removing the jumper will enable input through the SMA connector. For specific amplifier power-down polarity, please refer to the respective device data sheet.