Design Ideas power novel applications of simple circuits

This Design Idea employs the Microchip PIC10F222 single-chip microcontroller. You program this microcontroller’s internal memory using the MCLR pin. As the title, "Use the MCLR pin as an output with PIC microcontrollers," suggests, this Design Idea allows you to use the MCLR pin as an output pin during normal operation with the addition of a simple circuit.

You can use the circuit in "High-speed clamp functions as pulse-forming circuit"—a fast-response voltage limiter, or clamper—as a pulse-forming circuit. The input-voltage range is narrower than that of Schmitt-trigger circuits, because, at low input voltages, the voltage limitation becomes inactive, and the circuit operates as a linear amplifier.

Engineers pay too little attention to depletion-mode MOSFETs, which require no forward-biasing for normal operation and, moreover, require gate potentials below the source. These valuable properties of depletion-mode MOSFETs suit them for a role in "Depletion-mode MOSFET kick-starts power supply."

"Simple continuity tester fits into shirt pocket" describes a handy continuity tester with two modes of operation: It may sound if it detects continuity between its two probes, or it may sound when it detects no continuity. The second option permits testing for intermittent cable breaks. The tester is fully protected against being applied to live circuits.

Generating the high voltage needed for driving a white LED from a low-voltage power supply basically requires some form of an electronic oscillator to act as the heart of a switch-mode supply. One of the simplest is a piezoelectric buzzer. An unusual application of a piezoelectric transducer serves as an oscillator and drives a white LED in "White LED shines from piezoelectric-oscillator supply."