Circuits@Home

Linear power supply

Several days ago I received an e-mail from Larry Owens, my fellow Coloradoan. Larry is Hi-Fi enthusiast; he built USB isolator kit and made very elegant and clever modification to it – a linear power supply. Larry’s design fits on existing board footprint.

Here is a quote from Larry’s e-mail:

Thought you might like to see what a little creativity can yield — did not fancy a SMPS’s noise, but wanted to be able to handle various battery sources. Since the off-board supply would be rather quiet, just selected a plain old 7805C (found in drawer, able to dissipate plenty of heat w/ 12v+ supplies and full 500mA USB loads). Thought a power-up LED would be nice too… …the challenge was to find existing pads for all components without having to use any cut/jumps… do consider that outcome lucky at the least…

Take a look at the title picture (click on it to make it bigger). TO-220 next to the barrel connector is old trusty 7805 linear regulator. Small bypass capacitor is soldered between output and ground pins of it. Input and output pads are occupied with electrolytic caps, 100 ohm ( @100 MHz ) ferrite bead sits on inductor pads. Finally, a small LED is mounted in place of 3300pF cap with current-limiting resistor across LT1376 pins 7 and 8.

This is it – simple, elegant and very useful. Thanks again, Larry for sharing the design and very nice and clear picture!

Oleg.