A buffer is typically required to drive the resolver’s low-impendence inputs. This excitation buffer can be implemented in many ways, two of which are shown here. The first circuit is commonly used in automotive and industrial designs, while the second simplifies design by replacing the standard push-pull architecture with a high output current amplifier.
The high-current driver shown in Figure 11 amplifies and level shifts the reference oscillator output. The driver uses an AD8662 dual, low-noise, precision op amp and a discrete emitter follower output stage. A duplicate buffer circuit provides a fully differential signal to drive the resolver’s primary winding.