If dual supplies are used, then the GND pin can be connected to a hard ground (0 V) (as shown in Figure 6-2). However, if only a single supply is used, this pin must be set to a voltage of one V_BE (≈0.7 V) or greater, or more commonly, mid rail, by a stiff, low impedance source. This precludes applying a resistive voltage divider to the GND pin for this purpose. Figure 6-6 shows one way that this can be done.

Figure 6-6 Using an Op Amp to Bias the GND Pin to ½ V⁺ for Single Supply Operation

In Figure 6-6, the op amp circuit pre-biases the GND pin of the buffer for single supply operation.

The GND pin can be driven by an op amp configured as a constant voltage source, with the output voltage set by the resistor voltage divider, R₁ and R₂. It is recommended that These resistors be chosen so as to set the GND pin to V⁺/2, for maximum common mode range.