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91 lines
3.1 KiB
91 lines
3.1 KiB
<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
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<html lang="en">
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<head>
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<meta http-equiv=Content-Type content="text/html; charset=windows-1252">
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<title>The Class-A Amplifier Site - Current Boosted Regulator</title>
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<link rel="StyleSheet" href="class-a.css" type="text/css" media="screen, print">
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<link rel="shortcut icon" type="image/ico" href="favicon.ico">
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</head>
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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
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page was last updated on 14 October 2001</span></p>
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<p><b><span style='color:blue'><a href="index-1.htm" title=index-1.htm>[ Back
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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'>Current
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Boosted LM317/LM337 Regulator</span></b></p>
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<p> </p>
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<p> </p>
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<p>The LM338K is a relatively expensive device (at least here in the UK) and may
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not be easy to find in certain locations. The current boosted 7815/7915
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regulator circuit in the 1996 article is an alternative, but this requires
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power resistors in the supply line. It also has reduced regulation due to the
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voltage lifting arrangements necessary to provide a 22V output from a 15V
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regulator.</p>
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<p> </p>
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<p>The following current boosted LM317/LM337 circuit is essentially that
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included on several manufacturers' datasheets. The capacitor values have been
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changed from those on the datasheets to reflect the use of electrolytic
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capacitors as opposed to tantalum devices (I'm not happy with the reliability
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of tantalum capacitors even though they do have some desirable characteristics)
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and the transistors types have been altered to ones that are more readily available.
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The capacitor values are not critical and may be halved or doubled to suit
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available components, though a minimum voltage rating of 35V should be
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observed.</p>
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<p> </p>
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<p>The circuit shown is suitable for supplying a single amplifier (2A quiescent
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current). If two amplifiers are to be supplied from a single regulator, I
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recommend that the pass transistors (Q3, Q4) be duplicated using a parallel
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arrangement. In either case, a heatsink of between 2 and 3degC/W will be
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required for each transistor. The exact size of heatsink required should be
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determined whilst taking into account individual circumstances.</p>
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<p> </p>
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<p>VR1 & VR2 should be adjusted, under load, to give +/-22V supply rails.</p>
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<p> </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=691 height=732 src="jlhlm3x7cbfig1.gif"></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
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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 14/10/2001</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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