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