Subject: Re: Historical question: negative feedback and the op amp
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Thu, 14 Nov 2002 11:12:42 GMT
NNTP-Posting-Date: Thu, 14 Nov 2002 12:12:42 MET
see how your question finally has developed to a high-class discussion,
where everyone gets out these dusty DSP books and carefully checks his
arguments before sending them.
There are at least 3 main themes,
3. digital(with and without fb) vs. analog
I personally enjoy mainly point3. which is where it is happening now.
Certainly digital signal processing will revolutionize our technical
evolution as much as the invention of the transistor or operational
More and more new ideas like adaptive, convolution and lattice filters are
being refined to accomplish formerly impossible tasks.
On the other hand Chuck is right when promoting IIR-filters.
A minimum phase filter has the fastest possible response time and that is
what analog filters are (hopefully).
Only an IIR-filter can be equal, and then also the phase response will be
similar to the analog counterpart. (which means high frequencies will be
With digital filters you cannot shorten the filtering time with a faster
sampling and processing time, because the ratio of clock/filter frequency
gives the length of an filter, which is more accurate but not faster.
electronic hardware designer
"Mike" schrieb im Newsbeitrag
> "Ban" wrote in message
> > "Mike" schrieb im Newsbeitrag
> > news:hBnA9.5273$XF5.firstname.lastname@example.org...
> > Feedback in itself is more a cure for the unlinearity and other
> > shortcomings, nowadays it is no more needed, digital circuits work so
> > precise, they do not require feedback. Feedback is an antique thing, it
> > wasts power and a *lot* of speed. It is just a crutch not something we
> > should cherish.
> Hmmm... I can't think of any way to build a PLL equivalent that doesn't
> feedback, whether it's analog or digital. Without that "crutch," your disk
> drive won't spin at the correct speed, and you won't be able to recover
> from it. Your cell phone won't work, because the receiver won't be able to
> track the incoming signal. Even your land based telephone won't work,
> because nothing will be able to recieve the SONET/SDH signal at the other
> end. Your computer network won't work at all. Digital won't help you, no
> matter how accurate it is: you have to be able to track another signal,
> to do that, I'm not aware of any mechanism besides feedback. Are you?
> Speaking of analog vs digital, virtually every communication channel,
> whether it's a disk drive or a cell phone or a network link or a DSL or
> cable modem, winds up with an analog signal at the receiver, and often at
> the transmitter as well. Even many of the digital signals blasted across
> your motherboard are best thought of as analog.
> You might think analog is dead, but I find it to be a remarkably rich and
> fertile place for innovation and invention.
> -- Mike --