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<blockquote data-quote="John Roberts" data-source="post: 40328" data-attributes="member: 126">Re: High quality power amps with onboard DSP and load monitoring.Paralleling output devices in analog power amp stages is indeed routine above a certain power point, and more so since plastic packages replaced metal can transistors. The common practice is to use (small value) series resistor degeneration to improve sharing between devices. Paralleling saturated switch power devices, OTOH is not quite as simple or as common. I have asked people smarter than me about such things, and they say it can be done. That said I have never seen it done on any of the amps I was involved with pimping. In fact there are class D output topologies, variants on bridging where two output stages drive differentially, that were attractive precisely because they got to involve two times the power devices for twice the power dissipation while avoiding the need to parallel any devices. Twice the voltage swing was also a useful characteristic of that alternate topology. I don&#039;t doubt that this (paralleling saturated switches) can and is being done but it isn&#039;t common (AFAIK) in saturated switch power stages, so the posters concern is perhaps worth inspection, while the bottom line is how do they work in the field?&nbsp; If they had a serious reliability issue, the market would quickly find out. Second guessing under the hood decisions is good sport, and fodder for competing makers to attack, but not necessarily important, if the design is conservative and robust. JR</blockquote>

[QUOTE="John Roberts, post: 40328, member: 126"] Re: High quality power amps with onboard DSP and load monitoring. Paralleling output devices in analog power amp stages is indeed routine above a certain power point, and more so since plastic packages replaced metal can transistors. The common practice is to use (small value) series resistor degeneration to improve sharing between devices. Paralleling saturated switch power devices, OTOH is not quite as simple or as common. I have asked people smarter than me about such things, and they say it can be done. That said I have never seen it done on any of the amps I was involved with pimping. In fact there are class D output topologies, variants on bridging where two output stages drive differentially, that were attractive precisely because they got to involve two times the power devices for twice the power dissipation while avoiding the need to parallel any devices. Twice the voltage swing was also a useful characteristic of that alternate topology. I don't doubt that this (paralleling saturated switches) can and is being done but it isn't common (AFAIK) in saturated switch power stages, so the posters concern is perhaps worth inspection, while the bottom line is how do they work in the field? If they had a serious reliability issue, the market would quickly find out. Second guessing under the hood decisions is good sport, and fodder for competing makers to attack, but not necessarily important, if the design is conservative and robust. JR [/QUOTE]

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