Electrical transients can cause higher-than-normal voltages across a diode= use RC series circuit connected across the diode. | Power amplifiers Introduction Power devices & characteristics Power amplifier classes Power amplifier architecture AC & DC coupled amplifier Negative feedback in power amplifier Introduction Last amplifier stage - supply power load Typical: 1W - 100W Important parameters: Power-handling capacity Power efficiency Amplifier distortion Heat sinking Usually not considered to be linear amp. Classes: A, B, AB, C, D Power devices & characteristics Diode Power BJT Power MOSFET Thyristor (SCR-silicon controled rectifier) Insulated-Gate Bipolar Transistor (IGBT) Gate Turn-Off Thyristors MOS-Controlled Thyristor (MCT) Power devices & characteristics Power Diode Power diode: high forward-current capability Use: mainly as uncontrolled rectifiers Construction: usually use silicon Protection: must be protected against over current, over voltage, and transients. Choose a diode with a Vpeak reverse > Vexpected Current ratings use RC series circuit connected across the diode Power devices & characteristics Power BJT Power BJT: high forward-current capability, P=nW – n*100 KW => power Darlington transistors: small base current Use: for high power application Construction: usually use silicon Protection: must be protected against high current, high voltage. Overcurrent protection turns transistor OFF when Vce. Ic > preset values. => limits the base current during an external fault Overvoltage protection: overcurrent protection of a transistor is to connect an antiparallel diode across the transistor. Power devices & characteristics Power BJT example Power devices & characteristics Some power BJT applications Power devices & characteristics Power FET High forward-current capability, P=nW–n*100 W Use: as switch in power electronic applications Construction: usually use silicon Protection: must be protected against high current, high voltage. Figures: schematic diagram and device symbol Switching | Power amplifiers Introduction Power devices & characteristics Power amplifier classes Power amplifier architecture AC & DC coupled amplifier Negative feedback in power amplifier Introduction Last amplifier stage - supply power load Typical: 1W - 100W Important parameters: Power-handling capacity Power efficiency Amplifier distortion Heat sinking Usually not considered to be linear amp. Classes: A, B, AB, C, D Power devices & characteristics Diode Power BJT Power MOSFET Thyristor (SCR-silicon controled rectifier) Insulated-Gate Bipolar Transistor (IGBT) Gate Turn-Off Thyristors MOS-Controlled Thyristor (MCT) Power devices & characteristics Power Diode Power diode: high forward-current capability Use: mainly as uncontrolled rectifiers Construction: usually use silicon Protection: must be protected against over current, over voltage, and transients. Choose a diode with a Vpeak reverse > Vexpected Current ratings < Irecommend Electrical transients can cause higher-than-normal voltages
