Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: OP amp design Posted: Sun Sep 18, 2005 10:59
I am going to design a zero crossing detector
with using an op amp.
Then, I found a basic circuit from internet
that the circuit uses voltage divider from the main source (230 V) as
as input voltage (V+) for the op amp.
One thing that
I am not sure is, why it uses coupling capacitor instead of resistor
in the voltage divider ? What is the advantage of it ?
you in advance.
Post subject: Posted:
Sun Sep 18, 2005 11:10 am
Sorry for the small image.
Here I make
it bigger. Thanks.
OpAmp QuestionPosted: Mon Sep 19, 2005 11:53 am
It's a matter of
Resistors convert power=current*voltage into heat, capacitors
Why waste power?
Post subject: Re: OpAmp QuestionPosted: Mon Sep 26, 2005
It's a matter of numbers.
convert power=current*voltage into heat, capacitors don't.
removes any DC offsets from the generator and the 500k provides the
Post subject: Coupling
capacitorPosted: Wed Sep 28, 2005 5:44 pm
In most areas, the 230
V mains voltage comes from a transformer. Since transformers do not
pass DC, there should be *NO* DC offsets on the incoming voltage.
A resistor would, in fact, work in the circuit where the capacitor