SBOU268 November 2021 OPA593
Inputs to the EVM can be a voltage level or signal that is within the OPA593 specified input voltage range, relative to the gain setting and supply voltages applied to the EVM. BNC connectors are used at the J5 (VIN–) and J9 (VIN+) inputs for signal generators or a dc source. The inputs at J5 and J9 can be monitored at TP1 and TP4, respectively. Those two test points, along with the TP2 and TP5 grounds, can be used as alternate inputs if the BNC jacks cannot be used. Some sort of clip arrangement would be required to clip onto the test points.
To determine if the 49.9-Ω, 2-W R9 input resistor has a sufficient power rating for the intended RMS input voltage, apply the formula: Power = Voltage(RMS)2 / Resistance. Alternatively, an external higher-wattage BNC terminator can be connected at one of the EVM input connectors if there is a risk of damaging R9.
Furthermore, the EVM can be set to a –1 V/V inverting gain by employing the onboard 1-kΩ, 2-W resistors: R1 input resistor and RF2 feedback resistor. If the input voltage applied to VIN– is set to either 40 V or –40 V (±42.5 V supplies), these resistors will have to dissipate as much as 1.6 W each. The EVM uses these 2-W surface-mount resistors (wide 2512) to handle this higher power-dissipation case. Similarly, these two resistors have similar power dissipation when the EVM is set up for a noninverting gain of 2 V/V.