<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 10 (filtered)">
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{color:purple;
text-decoration:underline;}
span.emailstyle17
{font-family:Arial;
color:windowtext;}
span.EmailStyle18
{font-family:Arial;
color:navy;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.25in 1.0in 1.25in;}
div.Section1
{page:Section1;}
-->
</style>
</head>
<body lang=EN-US link=blue vlink=purple>
<div class=Section1>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Yes, the supplies are DC 5V; I just put pk-pk
so it wont be confused with -5V and 5V. And yes, I can make a schematic
of it; or for those of you who have the book “Practical Electronics For
Inventors”, its on page 264, fig. 8.12. Is it possible to put
attachments on emails on this forum?</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<div>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'>___________________<br>
Ray Xu<br>
<a href="mailto:rayxu@tx.rr.com" target="_blank">rayxu@tx.rr.com</a><br>
<a href="http://www.dprg.org" target="_blank">DPRG</a> member<br>
<a href="http://tech.groups.yahoo.com/group/oopic/" target="_blank">OOPic</a>
group member<br>
<a href="http://tech.groups.yahoo.com/group/SeattleRobotics/" target="_blank">Seattle
Robotics</a> group member<br>
<a href="http://rayxublogs.blogspot.com/" target="_blank">My Blog</a></span></font></p>
</div>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'>-----Original Message-----<br>
<b><span style='font-weight:bold'>From:</span></b> Kenneth Maxon
[mailto:kmaxon@qwest.net] <br>
<b><span style='font-weight:bold'>Sent:</span></b> </span></font><font size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>Thursday, July
31, 2008</span></font><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma'> </span></font><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'>9:33 PM</span></font><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'><br>
<b><span style='font-weight:bold'>To:</span></b> ray xu; dprglist@dprg.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> RE: [DPRG] Question about
electronic filters</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>The wording on the supply voltage is
a little suspect there. 5V Pk-Pk tends to indicate that AC wave forms are
being applied to the power rails of the device, which I suspect is not the
case. Possibly, the power rails are 5VDC and return or common at 0VDC?</span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>If the above assumption is correct,
then the 2'nd wording issue is 1V Pk-Pk which would indicate an AC waveform as
the input.</span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>The part that needs to be addressed
here is the configuration of the filter to make sure that an offset is applied
such that the output is not clipped. A DC offset can be added to the
signal being filtered with only a resistor or two in the op-amp configuration,
thus stopping the clipping problem. The interfering frequencies
generated by the clipping effect can have an impact on the efficiency of the
filter and possibly drive it close to saturation. The other answer is
that you may be supplying both +5VDC & -5VDC to the power rails of the
amplifier which can also work depending on the device.</span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>Lastly, if the power rails are
correct, and one of many standard filter configurations are used, the voltage
levels at the output can be completely independent from those at the power
rails. One needs more information about the configuration of the
supporting components (connectivity, type, etc) before the question can be
answered. Most simple single stage filter designs the output *IS*
independent from the supply rails, and the gain (near DC frequencies) is set by
the external components and their arrangements as well. One of the
parts to look at on the data sheet for the op-amp is the bandwidth-gain
product. This will specify the derating of gain vs frequency for
approximately linear operation of any given op-amp.</span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>Likely to get a full answer out of
the group, you'll need to grab paint or some other common tool, make a drawing
of the schematic in use and post it out on the web with a link to it for people
to evaluate as there are many thousands of ways to implement op-amp filter
circuits and say ~10+ are quite common for simple filters...</span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>-Kenneth</span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<p class=MsoNormal style='margin-right:0in;margin-bottom:12.0pt;margin-left:
.5in'><font size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>-----Original
Message-----<br>
<b><span style='font-weight:bold'>From:</span></b> dprglist-bounces@dprg.org
[mailto:dprglist-bounces@dprg.org]<b><span style='font-weight:bold'>On Behalf
Of </span></b>ray xu<br>
<b><span style='font-weight:bold'>Sent:</span></b> </span></font><font size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>Thursday, July
31, 2008</span></font><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma'> </span></font><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'>9:14 PM</span></font><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'><br>
<b><span style='font-weight:bold'>To:</span></b> dprglist@dprg.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [DPRG] Question about
electonic filters</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>I just have a general question about
electronic narrow bandpass filters. For example I have a filter with a
“pass” frequency of 200kHz. I build it using an op-amp with
its supply 5V Pk-Pk. I input a 200kHz frequency with a 1V Pk-Pk.
Would the output be 5V Pk-Pk or just its original 1V?</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face=Arial><span
style='font-size:12.0pt;font-family:Arial'>___________________<br>
Ray Xu<br>
<a href="mailto:rayxu@tx.rr.com" target="_blank">rayxu@tx.rr.com</a><br>
<a href="http://www.dprg.org" target="_blank">DPRG</a> member<br>
<a href="http://tech.groups.yahoo.com/group/oopic/" target="_blank">OOPic</a>
group member<br>
<a href="http://tech.groups.yahoo.com/group/SeattleRobotics/" target="_blank">Seattle
Robotics</a> group member<br>
<a href="http://rayxublogs.blogspot.com/" target="_blank">My Blog</a></span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
</body>
</html>