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Ideas for Design: Vol. 1, No. 4

This round of Ideas for Design articles highlights another use for the venerable LM555 timer as well as JFET amplifiers and distortion, a synthesized inductor, and improved power-factor correction.

Download Ideas for Design: Vol. 1, No. 4 in PDF format.

This round of Ideas for Design articles highlights another use for the venerable LM555 timer as well as JFET amplifiers and distortion, a synthesized inductor, and improved power-factor correction.

JFET Follower Amplifier Cancels Distortion

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Many improvements to the follower circuit have been proposed over the years. The White cathode follower doubles the output current and makes the transfer function more linear. Adding a common-base amplifying stage (current follower) significantly improved the White follower’s power-supply rejection ratio.

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Synthesized Inductor Delivers Maximum Power Transfer

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To transfer maximum power from a circuit to a load, the load’s resistance, RL, must match the source resistance. In the case of a complex load, ZL, and a resistive source, this transfer can require the use of a bulky inductor. This idea shows how to replace the physical inductor with a smaller synthesized inductor.

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Improved Power-Factor Corrector Further Minimizes Miller Effect

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Adding a discharge path to the upper MOSFET of a cascode circuit significantly reduces the unavoidable Miller effect and thus the PFC performance of a power supply's front end can be improved.

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LM555 Makes Inexpensive Power Driver

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The venerable 555-type timer makes an effective driver for power MOSFETs, but you have to understand the drive situation when selecting the correct variation of the basic timer. This idea shows how the wrong choice led to unreliable operation and failure, and the basic analysis that points to the correct choice.

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