<div dir="ltr">Thanks Bernie!</div><br><div class="gmail_quote"><div dir="ltr">On Thu, Nov 1, 2018 at 8:06 PM Bernard Arthur Hutchins, Jr <<a href="mailto:bah13@cornell.edu">bah13@cornell.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">




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<span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:black">It is good that Atsushi Maeda found the difficultly to be only that of misidentifying a component.<span> 
</span>90-degree PDNs are very INSENSITIVE to component tolerance variations (because they have only real-valued poles).<span> 
</span><span> </span>A moderate amount of care should assure a near-nominal performance – they just work – no tweaking.<span> 
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<span style="font-size:12.0pt;font-family:"Arial",sans-serif">An exception to this rosy picture occurs when we use an extremely large bandwidth to minimize end phase errors – say 5000:1.<span>    
</span>The poles have a corresponding spread and so do the RC products of the individual sections.<span> 
</span>In attempting to keep resistors in a range of perhaps 5.1k to 100k, capacitors may spread outside a corresponding desired spread range of perhaps 330 pfd to 0.05 microfarad (too small means stray capacitance matters, too large that caps are physically
 too large).<span>  </span>Happily I found some 30 years ago that by pairing the poles, largest to smallest, using 2dn-order secions nsead of first, the spread range is reduced to near unity.<span> 
</span>See:</span></p>
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<span style="font-size:12.0pt;font-family:"Arial",sans-serif"><a href="http://electronotes.netfirms.com/EN168-90degreePDN.PDF" id="m_-560840417882569333LPlnk43006" class="m_-560840417882569333OWAAutoLink" target="_blank">http://electronotes.netfirms.com/EN168-90degreePDN.PDF</a><span> 
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<a id="m_-560840417882569333LPUrlAnchor_15411234973900.9855665940552767" href="http://electronotes.netfirms.com/EN168-90degreePDN.PDF" style="text-decoration:none" target="_blank">LARGE SPREAD OF CAPACITOR VALUES; - Netfirms</a></div>
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<a href="http://electronotes.netfirms.com" target="_blank">electronotes.netfirms.com</a></div>
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THE DESIGN OF WIDEBAND ANALOG 90° PHASE DIFFERENCING NETWORKS WITHOUT /\ LARGE SPREAD OF CAPACITOR VALUES;-by Bernie Hutchins INTRODUCTION: The design of wideband 90° phase differencing networks is fundamental to the</div>
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<span style="font-size:12.0pt;font-family:"Arial",sans-serif">This discussion along with several related entries is on the Electronotes site as misc. items.
<span>  </span>As a bonus, you cut the number of op-amps<span> 
</span>in half.<span>  </span>Only reasonable way to design these – or so it seems to me.</span></p>
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<span style="font-size:12.0pt;font-family:"Arial",sans-serif">Bernie<span>  
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div>Quincas Moreira<br>Synth Diy Guy</div></div></div>