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99 lines
4.0 KiB
99 lines
4.0 KiB
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<title>The Class-A Amplifier Site - A Simple Voltage Regulator</title>
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<body background="slate.jpg" bgcolor="#E8E8E8" lang=EN-GB link=blue vlink=blue>
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<div class=Section1>
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<p align=right style='text-align:right'><b>The Class-A Amplifier Site</b></p>
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<p align=right style='text-align:right'><span style='font-size:10.0pt'>This page was last updated on 17 May 2001</span></p>
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<p align=left style='text-align:left'><b><span style='color:blue'><a
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href="index-1.htm" title=index-1.htm>[ Back to Index ]</a></span></b></p>
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<p><b> </b></p>
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<p align=center style='text-align:center'><b><span style='font-size:20.0pt'>A Simple Voltage Regulator</span></b></p>
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<p> </p>
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<p> </p>
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<p>The following diagram is provided for anyone who would like to include a voltage regulator but who does not want to use one of the ic versions (as in the updated, regulated supply for the 1996 design). This is a very basic regulator circuit, without any additional features such as foldback current limiting, and does not have the same performance as an ic regulator.</p>
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<p> </p>
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<p align=center style='margin:0cm;margin-bottom:.0001pt;text-align:center'><img
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border=0 width=722 height=656 src="jlhvoltregfig1.gif"></p>
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<p> </p>
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<p> </p>
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<p><b>Notes</b></p>
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<p> </p>
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<p>The TIP2955/TIP3055 transistors should be satisfactory for a power supply feeding a single amplifier. If two amplifiers are to be fed from a single power supply, these transistors should be changed to higher power devices such as the MJ2955/2N3055. Adequate heat-sinking must be provided for whichever transistors are used.</p>
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<p> </p>
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<p>R9 and R10 can be replaced with a 10k preset potentiometer (or a 5k potentiometer in series with a 5k6 fixed resistor) to provide adjustment of the output voltage.</p>
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<p> </p>
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<p>As with the capacitance multiplier circuit, Q2 and Q4 can be changed to a complimentary feedback pair arrangement, if required, to allow the use 2N3055s as the pass device in both halves of the supply (see the <a href="jlhcapmult.htm" title="The Capacitance Multiplier">capacitance multiplier</a> page for details). If this done, R9 and R10 must be made variable to allow the supply rails to be set to equal (but opposite) voltages. </p>
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<p> </p>
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<p>Zener diodes of a different voltage rating can be used for ZD1 and ZD2, but the value of R9 and R10 will need to be adjusted to maintain the +/-22V output.</p>
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<p> </p>
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<p>For different output voltages or a different Zener diode voltage, the output voltage can be calculated from the following equations:</p>
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<p> </p>
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<p style='text-indent:21.8pt'>+V<span style='font-size:8.0pt'>OUT</span> = ((R7 + R9) / R9) * (V<span style='font-size:8.0pt'>Z</span> + 0.6)</p>
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<p> </p>
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<p style='text-indent:21.8pt'>-V<span style='font-size:8.0pt'>OUT</span> = ((R8 + R10) / R10) * (V<span style='font-size:8.0pt'>Z</span> + 0.6)</p>
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<p> </p>
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<p align=left style='text-align:left'>where +V<span style='font-size:8.0pt'>OUT</span>
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and -V<span style='font-size:8.0pt'>OUT</span> are the required supply rail voltages and V<span style='font-size:8.0pt'>Z</span> is the Zener voltage.</p>
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<p> </p>
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<p> </p>
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<p><b><span style='color:blue'><a href="index-1.htm" title=index-1.htm>[ Back to Index ]</a></span></b></p>
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<p> </p>
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<p> </p>
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<p><b><span style='font-size:8.0pt'>HISTORY: </span></b><span style='font-size:8.0pt'>Page created 13/05/2001 </span></p>
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<p><span style='font-size:8.0pt'>16/05/2001 Diagram amended to correct polarity of D6, Resistor numbering corrected in voltage equation </span></p>
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<p><span style='font-size:8.0pt'>17/05/2001 Minor text changes. Second voltage equation added</span></p>
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<p><b><span style='font-size:8.0pt'> </span></b></p>
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</div>
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</body>
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</html>
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