jbl hartmann audio free download

File name JBL-Class-D amplifier.pdf

harman consumer group SERVICE CENTER TRAINING GUIDE Servicing Class D Amplifiers And The Theory of Operation Page 2 Introduction to Class D Amplifiers I. A Brief Description of Other Audio Amplifier Classes Class A · Class A amplifiers are biased. The signal operates in the linear region between cutoff and saturation. · The output devices conduct continuously, the bias current flows in the output devices at all times. · In Class A operation, both devices are always on. There is never a time when one output or another is turned off. · Class A is the most inefficient of all power amplifier designs. · Class A amplifiers are large, very heavy and run very hot. All of this is due to the amplifier constantly operating at full power. · Class A designs are the most linear, with the least amount of distortion. Harman Consumer Group 250 Crossways Park Dr. Woodbury, New York 11797 Email [email protected] Web www.harmanservice.com Page 3 I. A Brief Description of Other Audio Amplifier Classes (cont'd.) Class B · Class B operation is the opposite of Class A. Both output devices are never allowed to be on at the same time. · The output devices have no bias (.6 volts is needed to bias each device). · Each output device is on for exactly one half of the time. Class B designs have high efficiency but poor linearity; this is due to extreme crossover distortion. Harman Consumer Group 250 Crossways Park Dr. Woodbury, New York 11797 Email [email protected] Web www.harmanservice.com Page 4 I. A Brief Description of Other Audio Amplifier Classes (cont'd.) Class A/B · Class A/B is a combination of Class A and Class B. · Class A/B operation allows both devices to be on at the same time that the outputs have a bias voltage, so current flows to the output devices more than half of the time but less than the full time of the output wave form. This is called bias, and bias eliminates extreme crossover distortion. Harman Consumer Group 250 Crossways Park Dr. Woodbury, New York 11797 Email [email protected] Web www.harmanservice.com Page 5 I. A Brief Description of Other Audio Amplifier Classes (cont'd.) Class C Class C is used in single frequency RF applications. (Radio) Class F There are no existing products that use this class of amplifier. (You could be the first!) Harman Consumer Group 250 Crossways Park Dr. Woodbury, New York 11797 Email [email protected] Web www.harmanservice.com Page 6 I. A Brief Description of Other Audio Amplifier Classes (cont'd.) Class G In Class G operation two power supplies' voltages are used. A Class A/B amp is connected to a low voltage rail and a diode transistor matrix. When the signal is greater than the lower voltage rail can supply, a transistor switch connects the output stage to a higher voltage rail. This involves changing the power supply voltage from a lower level to a higher level automatically when a larger output swing is required for large signal peaks. Harman Consumer Group 250 Crossway