Design Ideas: Circuit schematics, applications, software, videos contributed by electronic engineers from EDN

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Simple fixture statically tests programmable-gain amplifiers

Marián Štofka, Slovak University of Technology, Bratislava, Slovakia; Edited by Martin Rowe and Fran Granville --EDN, 6/26/2008
Using a simple fixture having a common ground point, you can statically test digital gain-programmable amplifiers.

Control system uses LabView and a PC’s parallel port

Carlos Alberto Aguilar Sández, Centro de Estudios Superiores del Estado de Sonora, Unidad sede San Luis Rio Colorado, Sonora, Mexico; Edited by Martin Rowe and Fran Granville --EDN, 6/26/2008
A National Instruments LabView diagrammatic program controls the operation of a metered parking lot.

General-purpose components implement USB-based data-acquisition system

V Gopalakrishnan, Indira Gandhi Centre for Atomic Research, Kalpakkam, India; Edited by Martin Rowe and Fran Granville --EDN, 6/26/2008
A serial ADC communicates with a PC's USB port through a serial-to-parallel converter and a USB-interface IC.

Small, simple, high-voltage supply features single IC

Alfredo H Saab and Tina Alikahi, Maxim Integrated Products, Sunnyvale, CA; Edited by Martin Rowe and Fran Granville --EDN, 6/26/2008
An output toroidal transformer with a low-voltage feedback winding enables a small, high-voltage supply that uses a single IC.

CMOS DACs act as digitally controlled voltage dividers

John Wynne and Liam Riordan, Analog Devices, Limerick, Ireland; Edited by Martin Rowe and Fran Granville --EDN, 6/26/2008
You can employ a DAC to operate as a digitally programmable resistor from a single supply.

Precision temperature controller has thermal-gradient compensation

W Stephen Woodward, Chapel Hill, NC; Edited by Charles H Small and Fran Granville --EDN, 6/12/2008
An electronic work-around cancels the effects of thermal gradients in the load's thermal impedances.

Programmable current source requires no power supply

John Guy, National Semiconductor, Santa Clara, CA; Edited by Charles H Small and Fran Granville --EDN, 6/12/2008
A programmable current source is useful for creating I-V curves, charging and discharging batteries, preloading power supplies, and many other applications.

Pulse-width modulator has digital control

S Vinay Kumar, Mysore, India; Edited by Charles H Small and Fran Granville --EDN, 6/12/2008
Operating at 1 Hz, this pulse-width modulator has digital control.

Microcontroller controls analog phase shifter

Nick Ierfino, IGS Technologies, Montreal, PQ, Canada; Edited by Charles H Small and Fran Granville --EDN, 6/12/2008
By using a digital potentiometer in a phase-shift circuit, a microcontroller can precisely control phase shift.

Composite instrumentation amplifier challenges single-chip device for bandwidth, offset, and noise

Marián Štofka, Slovak University of Technology, Bratislava, Slovakia; Edited by Charles H Small and Fran Granville --EDN, 6/12/2008
By cascading the instrument amplifiers, you can achieve higher bandwidth and lower noise than with a single-chip amplifier.

Capacitive touch switch uses CPLD

Rafael Camarota, Altera, San Jose, CA; Edited by Charles H Small and Fran Granville --EDN, 5/29/2008
Using an Altera MAX IIZ CPLD, you can implement a touch-switch decoder with no external components.

Bit-shifting method performs fast integer multiplying by fractions in C

Aaron Lager, Panamax Furman, Santa Rosa, CA; Edited by Charles H Small and Fran Granville --EDN, 5/29/2008
Instead of calling math-library functions, you can multiply integers using bit shifting.

RS-232-to-TTL converter tests UARTs with a PC

Matthieu Bienvenüe, Malissard, France; Edited by Charles H Small and Fran Granville --EDN, 5/29/2008
A simple RS-232-to-TTL converter tests UARTs using a PC's serial port for power.

Hot-swap circuit allows two computers to monitor an RS-232 channel

Jeff Patterson, All Weather Inc, Sacramento, CA; Edited by Charles H Small and Fran Granville --EDN, 5/29/2008
A hot-swap serial-interface circuit allows two computers to monitor all the traffic on an RS-232 port.

Improved laser-diode-clamp circuit protects against overvoltages

James Zannis, Baulne-en-Brie, France; Edited by Charles H Small and Fran Granville --EDN, 5/29/2008
Adding a bipolar transistor to a JFET laser-diode clamp protects high-current laser diodes.

Tiny microcontroller hosts dual dc/dc-boost converters

Dhananjay V Gadre, Netaji Subhas Institute of Technology, New Delhi, India; Edited by Charles H Small and Fran Granville --EDN, 5/15/2008
An Atmel AVR microcontroller can serve as the PWM controller for two dc/dc converters that provide high voltages from a two-cell supply.

Small capacitor supports telecom power supply during brownouts

Samuel Kerem, Rockville, MD; Edited by Charles H Small and Fran Granville --EDN, 5/15/2008
By using a charge pump, the energy stored in a small capacitor can support the operation of a "brick" telecom power supply during brownouts.

Cross-coupled gates prevent push-pull-driver overlap

Richard Rice, Oconomowoc, WI; Edited by Charles H Small and Fran Granville --EDN, 5/15/2008
Cross-coupled gates in the push-pull drive of a center-tapped transformer's primary prevent overlap.

Save valuable picoseconds using ECL-wired OR

Glen Chenier, TeeterTotterTreeStuff, Allen, TX; Edited by Charles H Small and Fran Granville --EDN, 5/15/2008
Substituting wire-OR connections for an XOR/XNOR ECL gate allows the circuit to meet stringent timing contraints.

Circuit and software provide accurate recalibration for baseline PIC microcontroller’s internal oscillator

Noureddine Benabadji, University of Sciences and Technology, Oran, Algeria; Edited by Charles H Small and Fran Granville --EDN, 5/1/2008
A simple circuit and an assembly-language program allow you to recalibrate the internal oscillator of a PIC microcontroller.

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