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.