Output circuit

A motor driving apparatus comprising:

• a logic unit configured to receive a control signal for a motor as an input signal;
• a first output terminal connected to one terminal of a coil of the motor;
• a second output terminal connected to the other terminal of the coil of the motor;
• a first pre-driver including a high-side transistor and a low-side transistor connected in series between a first terminal at which the electric potential is set to a fixed level and a second terminal, the ON/OFF operations of which are controlled in a complementary manner according to a control signal output from the logic unit, and configured to output, as a first driving signal, the electric potential at a connection node that connects the two transistors;
• a second pre-driver having the same configuration as that of the first pre-driver, and configured to output a second driving signal;
• a constant voltage circuit configured to stabilize the voltage at each of the second terminals of the first and second pre-drivers at a predetermined voltage;
• and
• an H-bridge circuit including a first power transistor arranged between the first output terminal and a first terminal at which the electric potential is set to a fixed level, and configured to be controlled according to the first driving signal output from the first pre-driver, a second power transistor arranged between the second output terminal and the first terminal at which the electric potential is set to the fixed level and configured to be controlled according to the second driving signal output from the second pre-driver, a third power transistor arranged between the first output terminal and a third terminal set to a fixed electric potential that differs from the electric potential at the first terminal, and a fourth power transistor arranged between the second output terminal and the third terminal,
• wherein the constant voltage circuit comprises
• an output transistor arranged between the second terminal and the third terminal at which the electric potential is set to the fixed level,
• a differential amplifier configured to adjust the voltage to be applied to a control terminal of the output transistor such that the electric potential at the second terminal approaches a predetermined target value, and
• a feedback capacitor arranged between the second terminal and the control terminal of the output transistor.