Balun Transformers -  Application Note. . .  [MiniCircuits.com]

Caps Provide Voltage Boost to Series Regulator -  This circuit adds some capacitors and diodes to a traditional transformer type series regulator circuit to extend the normal operating range. It can insure regulation during low line voltage conditions or it can squeeze a few more watts out of a plug-in-the-wall power adapter power supply . . . [Circuit by David A. Johnson P.E.,  01/01/98]

Classic Plus & Minus DC Power Supply -  This is a classic example of a regulated DC power supply that produces both a positive 15v and a negative 15v from a 20vac wall adapter . . . [Circuit by David A. Johnson P.E.,  10/16/05]

Connect Line-Level Signal to Phono Input  -  The circuit does two functions: signal level attenuation and inverse RIAA filtering. The signal attenuation is needed to convert the 500 mV signal to 2. 5 mV signal. The inverse-RIAA filtering is needed to make the frequency response of the system flat (same equalization that is used when music is transferred to vinyl in the studio). The picture blow shows the frequency response of the ideal inverse-RIAA filter. . . 

Everything you wanted to knoW about wideband, low-frequency transformers -  11/23/00 EDN Design Idea   Wideband, low-frequency transformers are useful components in various passive circuits, such as the return-loss bridge ( Reference 1 , Figure 2 ). Figure 1a shows a conventional transformer. If you connect the transformer windings. . .  [by Richard Kurzrok, Queens Village, NY]

Floating Supply for LCD Panel Meter -  includes several designs, scroll down to find this one. Did you ever install one of those low-cost LCD panel meters in a project only to discover that it requires a floating power supply? I just did! The meter cannot share a DC ground with the voltage to be measured. The above circuit came to the rescue. It draws about 4 or 5 mA from the 9 volt supply and can supply up to 2 mA at 9 volts to the LCD meter or other load but the two capacitors isolate the grounds. Works like a champ!. . .  [Charles Wenzel (unless otherwise noted)]

Flyback circuit provides isolated power conversion -  01/07/99  EDN Design Idea (contains several designs, scroll to find this one)   A common requirement in telecommunications systems is to convert an unregulated 48V line to an isolated, accurate dc supply voltage. The circuit in Figure 1 provides a 5V, 15W output. The circuit uses a UCC3809 primary-side controller, which can also control other single-ended converters. The topology uses peak-current-mode control with a fixed-frequency oscillator. The design is cost-efficient, because it assumes that compensation of the voltage loop occurs on the secondary side, where you would place the error amplifier and reference anyway. By eliminating a primary-side amplifier, you reduce system cost and complexity. . . .  [by Philip Cooke, Unitrode Corp, Merrimack, NH]