Sony ST-SA50ES - Am/fm Tuner Background tecnico - Pagina 13

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The power MOS FETs in Sony's STR-DA7100ES are of a dramatically

different design, 50 to 70% thinner than the transistors used for the DA9000ES.

Even more important is the top molding of the transistor package, which is now

80% thinner than the previous design. The plastic itself is a resin of high thermal

conductivity, designed from the outset to encourage the flow of heat, not block it.

This thermal design—which runs counter to every practice in traditional

amplifiers—makes perfect sense considering the low heat generation of Sony's

S-Master Pro digital amplifier.

Sony takes advantage of this thermal design by coupling the heat sink to

the top of the MOS FET transistors, leaving the bottom to face a four-layer circuit

board, on which the transistors are surface mounted. Where most amplifiers

require thick aluminum heat sinks with many ribs to radiate the heat, the STR-

DA7100ES can use a single, simple sheet of metal with no ribs at all!

Extreme close-up of a single MOS FET output transistor (middle),

bonded to the L-shaped bracket of the heat sink. The transistor is

surface mounted to a four-layer circuit board (bottom).

On the left, the STR-DA7100ES power amplifier without the heat sink.

The four large black ICs in the middle are Sony's S-Master Pro 32-bit

LSIs, the CXD9773Q. On the right, the same circuit board with heat

sink in position.

Again, this runs counter to previous design practices for traditional

amplifiers. Typically, output transistors generate so much heat that they need to

ES Receivers v1.0

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