Often, applications must level-shift a ground-referenced signal to a non-ground voltage. Configurations in Figure 8-10 and Figure 8-11 show two different ways of level-shifting a signal by using the OPA862 without having to use external resistors, saving board cost and space. These configurations leverage the fixed noninverting gain-of-2 configuration of A2 and the summing configuration of A1 to level-shift the signal at VOUT–. The internal resistors of the OPA862 are extremely well-matched to maintain the gain-of-2 accuracy of A2. Similarly matched external resistors can add significant cost to the system and often are more expensive than the amplifier itself.

Apart from the polarity of the V_DC-shift at the output, a key difference between the configurations of Figure 8-10 and Figure 8-11 is that in the case of Figure 8-10, V_DC only must be capable of driving the I_B of A1 but in the case of Figure 8-11, V_DC must be capable of driving higher currents, as given by I = V_DC / R_G when a noninverting input of A1 is grounded.

Figure 8-10 Level-Shifting With a DC Source of Polarity Opposite to the Desired DC Shift

Figure 8-11 Level-Shifting With a DC Source of Polarity Same as the Desired DC Shift