Compact 200 W Output Stage
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Published in issue 345, July 2005
There is no doubt that this small power amp packs a punch. It is capable of delivering a healthy 200 W into 4 Ohm. Into 8 Ohm it can still output 125 W.
These large power outputs are made possible through the use of Darlington transistors made by Sanken, the SAP16N and its opposite number, the SAP16P (in our prototype we used their predecessors, the SAP15N and P, because the SAP16 versions were not available at that time). These power transistors have an emitter resistor built in, as well as a diode for temperature compensation. Because of this, the whole emitter follower stage has just two components (and a preset for setting the quiescent current, shown in the circuit).
Resistors:
R1, R19 = 470
R2, R22 = 10k
R3, R4, R8, R9 = 47
R5, R6, R10, R11, R15, R18 = 2k2
R7, R12 = 220
R13, R16 = 1k2
R14, R17 = 39k
R20, R21 = 15k
R23, R24 = 100
R25 = 1k
R26, R27 = 10 1W
P1,P2,P3 = 250 preset
Capacitors:
C1,C2,C3 = 1nF
C4, C5 = 10µF 63V radial
C6 = 47pF
C7 = 220pF
C8 = 33nF
C9, C11 = 1000µF 63V radial
C10, C12 = 100nF
Inductors:
L1 = 8 turns 1.5mm dia. ECW, inside diameter 10mm.
Semiconductors:
D1-D6 = 1N4148
T1 = 2SC3381 (Toshiba) (Huijzer; Segor Electronics)
T2 = 2SA1349 (Toshiba) (Huijzer; Segor Electronics)
T3,T4,T9 = 2SA1209 (Sanyo) (Farnell # 410-3841)
T5, T8 = BF245A
T6, T7, T10 = 2SC2911 (Sanyo) (Farnell # 410-3853)
T11 = SAP16N (Sanken) or SAP15N (Farnell # 410-3749)
T12 = SAP16P (Sanken) or SAP15P (Farnell # 410-3750)
Miscellaneous:
K1-K5 = 2-way spade terminal, PCB mount, vertical
Heatsink <0.5 K/W
Mica washers for T11 en T12, e.g., Conrad Electronics # 189049.
4 wire links on PCB
PCB, ref. 054008-1
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Click below to download a PDF copy of this article from Elektor magazine. Please note. In view of the complexity of international markets, Elektor cannot guarantee the availability of components for this project.
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