Using a negative power supply can extend the common-mode range 14 V more negative than the supply used. For instance, a –10 V supply allows up to –24-V negative common-mode. Remember to keep the total voltage between the GND pin and V+ pin to less than 18 V. The positive common-mode decreases by the same amount.
The reference input simplifies this type of operation because the output quiescent bias point is always based on the reference connections. Figure 7-7 shows a circuit configuration for common-mode ranges from –24 V to 70 V.