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On 5/10/2016 9:11 AM, clipka wrote:
> Am 09.05.2016 um 23:30 schrieb Orchid Win7 v1:
>
>> I have to admit, I have frequently wondered why this *digital* device
>> has hundreds of *analog* components on it (mostly capacitors and
>> inductors). I mean, I get why they're on the motherboard rather than on
>> the silicon die, but why do you need them at all?
>
> To keep the primary components (mostly transistors) firmly within the
> range of operating parameters where they behave "digitally".
>
> Most of the capacitors are there to keep the supply voltages stable. You
> wouldn't believe how much noise a digital circuit feeds back into its
> power supply, and you don't want that noise to feed forward into other
> parts of the circuitry.
>
>> Is there a simple relationship between circuit design and heat output? I
>> mean, is it something as simple as number of switching elements and how
>> fast they switch per second? Or is it something more complicated?
>
> Power consumption (and hence heat output) of modern (i.e. FET-based)
> digital electronic circuitry mainly depends on the total number of
> transistors changing state every second, because that's when currents flow.
>
> However, the relationship between per-transistor switching frequency and
> power consumption is non-linear (presuming the circuitry is operated at
> its limits), since higher switching frequencies require faster charge
> transfers, which means shorter pulses of higher currents, which in turn
> also require higher voltages to drive them.
>
> In addition to this inevitable "payload" power consumption there will be
> various parasitic losses, such as from inevitable signal line
> inductivities and capacitances, as well as plain old leakage currents,
> all of which obviously get worse with increased operating voltages, chip
> area and complexity, but in /very/ non-linear ways.
>


-- 

Regards
     Stephen

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