Design and Analysis of Pulsewidth-Modulated Amplifiers for DC Servo Systems

The use of pulse width-modulated amplifiers for dc servo systems, in order to reduce the power dissipation in the output stage is proposed. The amplifier transistors can be switched in different sequences, and the amplifier will operate accordingly in three possible modes, namely the bipolar, the unipolar, and the limited unipolar modes. The principle of operation and the mathematical model for each case are described along with the special features of this amplifier which include the power dissipation in the motor and the selection of the switching frequency.