In this design example, two OPA593 precision op amps are configured as a unity gain buffers powered with a ±42.5-V dual supply. The input signal to either amplifier can range from –40 V to +39 V to remain in linear operation. The output of the amplifiers are connected together and a 3-V or 5-V logic signal, serving as the output select, is used to toggle between the enable and disable modes of operation. The logic control signal is directly applied to one OPA593 E/D pin, and an inverter gate is used to drive the other OPA593 E/D pin. Figure 8-3 shows a simplified representation of this circuit.

A clear benefit of this design is the high-voltage capability, along with the thermal protection, overcurrent protection, and current-limit features. The mux-friendly input of the OPA593 provides a full input differential range, avoiding the pitfalls of other amplifiers with traditional back-to-back diodes in this configuration. This design can also be reconfigured to include signal gain, but careful selection of the input and feedback resistors is required to minimize current leakage paths.