| This preamplifier regulator is
very straightforward, using the
Supertex LR8N3 high voltage regulator to provide regulated
base voltage for an NPN pass transistor. The Supertex LR8N3
was intended for regulation of the input to off-line switching
power supplies, but is readily deployed for audio use: |
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As the schematic shows, the pass transistor can
be an MJE3439, BU205A or BU208A -- the last of these is a TO-3
device and should be mounted off the PCB. The regulator with
BU205A should be satisfactory to regulate the input and screen stages of an audio
amplifier. It is important to heatsink Q1, even more
important to use the proper high voltage isolation on the
transistors since the collector is at a very high voltage. |
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The output voltage is determined by the ratio
of resistors R1 and R2:
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V(out) = |
(1.20 *( 1 + R2/R1)) + (Iadj
* R2) |
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where Iadj is typically 10 ľA. |
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Circuit Board:
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Results: |
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Bill of Materials: |
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