45 Watt Class B Amplifier

45 Watt Class B Amplifier

	Circuit diagram:
	Malzeme Listesi R1______________18K 1/4W Resistor
	R2_______________3K9 1/4W Resistor
	R3,R6____________1K 1/4W Resistors
	R4_______________2K2 1/4W Resistor
	R5______________15K 1/4W Resistor
	R7______________22K 1/4W Resistor
	R8_____________330R 1/4W Resistor
	R9,R10__________10R 1/4W Resistors
	R11,R12_________47R 1/4W Resistors
	R13_____________10R 1W Resistor
	C1_______________1µF 63V Polyester Capacitor
	C2_____________470pF 63V Polystyrene or Ceramic Capacitor
	C3______________47µF 25V Electrolytic Capacitor
	C4______________15pF 63V Polystyrene or Ceramic Capacitor
	C6_____________220nF 100V Polyester Capacitor
	C6_____________100nF 63V Polyester Capacitor
	D1,D2,D3,D4___1N4148 75V 150mA Diodes
	Q1,Q2________BC560C 45V 100mA Low noise High gain PNP Transistors
	Q3,Q4________BC556 65V 100mA PNP Transistors
	Q5___________BC546 65V 100mA NPN Transistor
	Q6___________BD139 80V 1.5A NPN Transistor
	Q7___________BD140 80V 1.5A PNP Transistor
	Q8__________2N3055 60V 15A NPN Transistor
	Q9__________MJ2955 60V 15A PNP Transistor
	Power supply circuit diagram:
	B 45W Amplifier Power Supply
	Malzeme Listesi
	R1_______________3K3 1/2W Resistor
	C1,C2_________4700µF 50V Electrolytic Capacitors
	C3,C4__________100nF 63V Polyester Capacitors
	D1_____________200V 8A Diode bridge
	D2_____________5mm. Red LED
	F1,F2__________4A Fuses with sockets
	T1_____________230V or 115V Primary, 25+25V Secondary 120VA Mains transformer
	PL1____________Male Mains plug
	SW1____________SPST Mains switch
	Comments:
	The main design targets for this amplifier were as follows:
	Output power in the 40 - 70W range
	Simple circuitry
	Easy to locate, low cost components
	Rugged performance
	No setup
	These goals were achieved by using a discrete-components op-amp driving a BJT complementary common-emitter output stage into Class B operation. In this way, for small output currents, the output transistors are turned off, and the op-amp provides all of the output current. At higher output currents, the power transistors conduct, and the contribution of the op-amp is limited to approximately 0.7/R11. The quiescent current of the op-amp biases the external transistors, and hence greatly reduces the range of crossover.
	The idea sprang up from a letter published on Wireless World, December 1982, page 65 written by N. M. Allinson, then at the University of Keele, Staffordshire.
	In this letter, op-amp ICs were intended as drivers but, as supply voltages up to +/- 35V are required for an amplifier of about 50W, the use of an op-amp made of discrete-components was then considered and the choice proved rewarding.
	The discrete-components op-amp is based on a Douglas Self design. Nevertheless, his circuit featured quite obviously a Class A output stage. As for proper operation of this amplifier a Class B output stage op-amp is required, the original circuit was modified accordingly.
	Using a mains transformer with a secondary winding rated at the common value of 25 + 25V (or 24 + 24V) and 100/120VA power, two amplifiers can be driven at 45W and 69W output power into 8 and 4 Ohms respectively, with very low distortion (less than 0.01% @ 1kHz and 20W into 8 Ohms).
	This simple, straightforward but rugged circuit, though intended for any high quality audio application and, above all, to complete the recently started series of articles forming the href="Page148.htm">Modular Preamplifier Control Center, is also well suited to make a very good Guitar or Bass amplifier. Enjoy!
	Notes:
	2N3055 and MJ2955 transistors were listed for Q8 and Q9 as the preferred types, but many different output transistors can be used satisfactorily: TIP3055/TIP2955, TIP35/TIP36, MJ802/MJ4502 amongst others.
	Discrete op-amp output transistors Q6 and Q7 do not require any heatsink as their cases remain at ambient temperature. Power transistors Q8 and Q9 should be mounted on a black, finned heatsink as usual.
	Technical data:
	Output power (1KHz sinewave):
	45 Watt RMS into 8 Ohms - 69W RMS into 4 Ohms
	Sensitivity:
	0.81V RMS input for 45W output
	Frequency response @ 1W RMS:
	15Hz to 23KHz -0.2dB
	Total harmonic distortion @ 1KHz:
	"c">  1W 0.008%                    "c">20W 0.008% "c"> 45W 0.016%
	Total harmonic distortion @10KHz:
	"c">1W 0.01% "c">20W 0.015% "c">45W 0.025%
	Unconditionally stable on capacitive loads

Malzeme Listesi

	R1______________18K 1/4W Resistor
	R2_______________3K9 1/4W Resistor
	R3,R6____________1K 1/4W Resistors
	R4_______________2K2 1/4W Resistor
	R5______________15K 1/4W Resistor
	R7______________22K 1/4W Resistor
	R8_____________330R 1/4W Resistor
	R9,R10__________10R 1/4W Resistors
	R11,R12_________47R 1/4W Resistors
	R13_____________10R 1W Resistor
	C1_______________1µF 63V Polyester Capacitor
	C2_____________470pF 63V Polystyrene or Ceramic Capacitor
	C3______________47µF 25V Electrolytic Capacitor
	C4______________15pF 63V Polystyrene or Ceramic Capacitor
	C6_____________220nF 100V Polyester Capacitor
	C6_____________100nF 63V Polyester Capacitor
	D1,D2,D3,D4___1N4148 75V 150mA Diodes
	Q1,Q2________BC560C 45V 100mA Low noise High gain PNP Transistors
	Q3,Q4________BC556 65V 100mA PNP Transistors
	Q5___________BC546 65V 100mA NPN Transistor
	Q6___________BD139 80V 1.5A NPN Transistor
	Q7___________BD140 80V 1.5A PNP Transistor
	Q8__________2N3055 60V 15A NPN Transistor
	Q9__________MJ2955 60V 15A PNP Transistor
	Power supply circuit diagram:
	Parts:
	R1_______________3K3 1/2W Resistor
	C1,C2_________4700µF 50V Electrolytic Capacitors
	C3,C4__________100nF 63V Polyester Capacitors
	D1_____________200V 8A Diode bridge
	D2_____________5mm. Red LED
	F1,F2__________4A Fuses with sockets
	T1_____________230V or 115V Primary, 25+25V Secondary 120VA Mains transformer
	PL1____________Male Mains plug
	SW1____________SPST Mains switch
	Comments:
	The main design targets for this amplifier were as follows:
	Output power in the 40 - 70W range
	Simple circuitry
	Easy to locate, low cost components
	Rugged performance
	No setup
	These goals were achieved by using a discrete-components op-amp driving a BJT complementary common-emitter output stage into Class B operation. In this way, for small output currents, the output transistors are turned off, and the op-amp provides all of the output current. At higher output currents, the power transistors conduct, and the contribution of the op-amp is limited to approximately 0.7/R11. The quiescent current of the op-amp biases the external transistors, and hence greatly reduces the range of crossover.
	The idea sprang up from a letter published on Wireless World, December 1982, page 65 written by N. M. Allinson, then at the University of Keele, Staffordshire.
	In this letter, op-amp ICs were intended as drivers but, as supply voltages up to +/- 35V are required for an amplifier of about 50W, the use of an op-amp made of discrete-components was then considered and the choice proved rewarding.
	The discrete-components op-amp is based on a Douglas Self design. Nevertheless, his circuit featured quite obviously a Class A output stage. As for proper operation of this amplifier a Class B output stage op-amp is required, the original circuit was modified accordingly.
	Using a mains transformer with a secondary winding rated at the common value of 25 + 25V (or 24 + 24V) and 100/120VA power, two amplifiers can be driven at 45W and 69W output power into 8 and 4 Ohms respectively, with very low distortion (less than 0.01% @ 1kHz and 20W into 8 Ohms).
	This simple, straightforward but rugged circuit, though intended for any high quality audio application and, above all, to complete the recently started series of articles forming the Modular Preamplifier Control Center, is also well suited to make a very good Guitar or Bass amplifier. Enjoy!
	Notes:
	2N3055 and MJ2955 transistors were listed for Q8 and Q9 as the preferred types, but many different output transistors can be used satisfactorily: TIP3055/TIP2955, TIP35/TIP36, MJ802/MJ4502 amongst others.
	Discrete op-amp output transistors Q6 and Q7 do not require any heatsink as their cases remain at ambient temperature. Power transistors Q8 and Q9 should be mounted on a black, finned heatsink as usual.
	Technical data:
	Output power (1KHz sinewave):
	45 Watt RMS into 8 Ohms - 69W RMS into 4 Ohms
	Sensitivity:
	0.81V RMS input for 45W output
	Frequency response @ 1W RMS:
	15Hz to 23KHz -0.2dB
	Total harmonic distortion @ 1KHz:
	1W 0.008 .20W 0.008 45W 0.016
	Total harmonic distortion @10KHz:
	1W 0.01. 20W 0.015. 45W 0.025%
	Unconditionally stable on capacitive loads