The ability to measure this current flowing in both directions is enabled by adding a unity gain amplifier with a V_REF, as shown in Figure 8-1. The output then responds by increasing above VREF for positive differential signals (relative to the IN – pin) and responds by decreasing below VREF for negative differential signals. This reference voltage applied to the REF pin can be set anywhere from 0 V to V+. For bidirectional applications, VREF is typically set at mid- scale for equal signal range in both current directions. In some cases, however, VREF is set at a voltage other than mid-scale when the bidirectional current and corresponding output signal are not required to be symmetrical.