The circuit shown in Fig. 62-15A is designed to drive a 15-V, two-phase, bipolar stepping motor, providing a bidirectional single level voltage across each winding at currents of up to 9.6 A. The circuit consists of two identical transistor bridge stages employing complementary npn and pnp devices. The transistor conduction sequence is determined by external control logic, and the circuit will interface directly with standard TTL.
A suitable control logic system is illustrated in diagram.