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<div class="moz-cite-prefix">For linear regulators like the 78xx
series you have a minimum 2-volt drop to account for the B-E
junctions of 2 transistors and the drop of a zener diode
(emitter-follower series current pass element, error amplifier and
voltage reference). So for a 5V regulator, you need to provide a
minimum 7V input; for a 3.3V regulator you need a minimum of 5.3V,
and so on.</div>
<div class="moz-cite-prefix"><br>
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<div class="moz-cite-prefix">There is a recent article in Circuit
Cellar magazine, Issue 364, Nov. 2020: "Voltage Regulators: Beat
The Heat", pg. 60 (From The Bench column by Jeff Bachiochi), that
explains about this.<br>
</div>
<div class="moz-cite-prefix"><br>
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<div class="moz-cite-prefix">On 11/15/20 8:07 PM, The MacDougals via
TriEmbed wrote:<br>
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<p class="MsoNormal">Can’t find ams1117-3.3 TI’s L1117-3.3 is a
direct replacement.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The data sheet shows 15v (max) for Vin and
nothing for min. What am I missing?<o:p></o:p></p>
<p class="MsoNormal"><a
href="https://www.ti.com/lit/ds/symlink/lm1117.pdf?HQS=TI-null-null-digikeymode-df-pf-null-wwe&ts=1605410881526"
moz-do-not-send="true">https://www.ti.com/lit/ds/symlink/lm1117.pdf</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">---> Paul<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>From:</b> Josh Wyatt
<a class="moz-txt-link-rfc2396E" href="mailto:dragojdw@gmail.com"><dragojdw@gmail.com></a> <br>
<b>Sent:</b> Sunday, November 15, 2020 7:47 PM<br>
<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Why not use something like AMS1117-3.3?
Minimum voltage on your 8 volt battery is going to be
something like 6VDC.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">-j<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Sun, Nov 15, 2020 at 7:38 PM The
MacDougals via TriEmbed <<a
href="mailto:triembed@triembed.org"
moz-do-not-send="true">triembed@triembed.org</a>>
wrote:<o:p></o:p></p>
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<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">How
do I find an LDO that operates on 8 – 8.8 v?<o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I
looked at a couple of datasheets and found linear
regulators that take 9v (max) input.<o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I
did not see a (min) spec for input v.<o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">How
can I tell if it works at 8?<o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">For
example:<o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><a
href="https://www.njr.com/electronic_device/PDF/NJM2888_E.pdf"
target="_blank" moz-do-not-send="true">https://www.njr.com/electronic_device/PDF/NJM2888_E.pdf</a><o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">--->
Paul<o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<pre class="moz-signature" cols="80">--
Scott G. Hall
Raleigh, NC, USA
<a class="moz-txt-link-abbreviated" href="mailto:ScottGHall1@GMail.Com">ScottGHall1@GMail.Com</a>
<i>Although kindness is rarely a job, no matter what you do it's always an option.</i>
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