313 results found, displaying items 1 - 20

I needed a simple LED indicator showing that a particular voltage level had been reached—specifically, that a capacitor had charged to a particular potential. I was convinced that there must be a way that a programmable zener diode, such as the TL431, could be used but I found no simple circuits. My first thought was just to connect a series current limiting resistor and LED to the cathode so that the LED would light when the reference potential was reached...

After Electronic Design asked me to contribute something to this special issue, all kinds of possibilities ran through my mind. After all, it had been 40 years since my first ED article, which was itself an Idea for Design (IFD), “Gated Amplifier Uses FET in Feedback Loop,” in the Jan. 4, 1968 issue. So, what’s an IFD? The snappy answer is that it’s one of Electronic Design’s most popular editorial features. But more germane...

Linear Technology’s Chief Technology Officer Robert Dobkin has been contributing Ideas for Design (IFDs) since his youth. He’s still enthusiastic about them. “I remember one I wrote when I was a kid. It was a current source that you could pulse on or off. I don’t know how many letters I got from that,” he said. “It had just two or three transistors in it, but it was really effective in terms of people coming back to me after reading it, which...

Electronic Design published my first Idea for Design, “AC-DC Converter Runs Off One Power Supply” (April 16, 1992, p. 93), more than 16 years ago (Fig. 1). It set a theme that I have continued to employ ever since—using the nifty venue of IFDs to present and develop new circuit design ideas and themes to the engineering community. Over the years, examples of some of those basic concepts and ...

After Electronic Design asked me to contribute something to this special issue, all kinds of possibilities ran through my mind. After all, it had been 40 years since my first ED article, which was itself an Idea for Design (IFD), “Gated Amplifier Uses FET in Feedback Loop,” in the Jan. 4, 1968 issue. So, what’s an IFD? The snappy answer is that it’s one of Electronic Design’s most popular editorial features. But more germane is...

FIGURE 1 DEMONSTRATES A one-way switchedcapacitor gain stage circuit, performing a voltage gain of AO = C1/C2 only during the decreasing trail of the input signal VI (with VJ = 0). During the positive signal variations, the output doesn’t change, thereby implementing an incremental peak-detector and accumulator circuit. This device can be used to measure the...

IN APPLICATIONS REQUIRING ABSOLUTE accuracy in the speed control of dc servo motors, there’s no substitute for the traditional tachometerbased feedback loop. But for somewhat less demanding situations, adequate accuracy often can be achieved without the complication and expense of a tach. This can be done by taking advantage of the built-in electromechanical constants of the motor itself. For example,...

SOME MULTI-STRING LED MODULES come with a common-anode configuration. The commonanode connection reduces the number of wires between the LED module and its driver from 2N to N+1, where N is the number of LED strings in the module. In this idea, we’ll drive a commonanode LED module while simultaneously limiting the LED string voltage when an LED string becomes open. Figure 1 shows the LT3496...

I WAS REMINDED RECENTLY of a tester I designed years ago. At the time, I wanted to build “The Ultimate Continuity Tester,” and I established a wish list of all the features I required: • A “real continuity” tester. Too many multimeters and sounders react at resistances as high as hundreds or even thousands of ohms, which makes them practically useless in many cases. Within a board or a system, there are always medium-conductivity...

IN CONSUMER ELECTRONICS APPLICATIONS, which tend to be lower in frequency and less demanding than typical clock-buffering applications, inexpensive high-speed op amps (~100-MHz bandwidth) can offer an attractive option in place of traditional clock buffers. High-speed amplifiers can be less expensive than traditional clock buffers, yet they’re able to accommodate a wide range of design configurations. For instance, one good alternative for...

THE SOARING COSTS OF fossil fuels, combined with environmental concerns like climate change, are driving the increased interest in renewable (“green”) energy. No energy source is “greener” than hydroelectric power, particularly small (“microhydro”) installations that involve minimal artificial water impoundment and associated environmental impact. Even with an adequate water source, however, efficient and cost-effective implementation of appropriate...

It’s fair to say there are really two kinds of reference designs. One is developed by chip companies that want a permanent foothold in an original device manufacturer’s high-volume platform in a consumer market. The other is produced by a chip company’s Web-based or downloadable PC tool that lets ordinary bench engineers mix and match ICs, simulate circuits, and obtain bills-of-materials (BOMs) and sometimes actual circuit board reference designs. ...

The filter described below is useful for detecting a signal that’s closely surrounded by spurs, even when the task is complicated by the frequency of the signal of interest wandering by a few percent. For example, in telecom, a pilot signal can originate from sources scattered around the world. Assume a 10.0-kHz signal of choice. Due to variations in oscillators, temperature conditions, and aging, a frequency deviation of ±200 Hz can be...

Galvanically (that is, optically or electromagnetically) isolated 4- to 20-mA current loops offer robust noise immunity and tolerate long cable runs. These advantages, combined with simple unshielded two-wire cabling, make this mature signaling standard popular for transmitting analog data in noisy industrial and process control environments. Unfortunately, the conversion of an analog voltage output to an isolated current-loop signal is relatively complicated. In...

This idea describes a white- LED (WLED) driver circuit controlled by a simple ambient light sensor (ALS). A typical application would be a brightness control for cell-phone backlighting. On a very sunny day, the brightness will increase to improve the visibility. The circuit uses the IA2505 four-channel WLED (Fig. 1). Each LED can be driven up to 20 mA, with the drive current...

A few simple components are all it takes to create an over-temperature alarm. The circuit in Figure 1 requires only an ordinary negative-temperature-coefficient (NTC) thermistor, two common ICs, and a handful of discrete components. The circuit uses a unipolar 12-V supply and consumes only a few milliamps in the idle state. This circuit is particularly suitable for monitoring the temperature of heatsink plates. ...

Privacy has become a major issue with the near ubiquitous availability of cell-phone cameras. Some people have called for a preliminary “privacy flash” that goes off just before the full flash in order to warn people that their picture is being taken. In fact, such a flash is required in Italy. You can implement a combination privacy- and full-flash light using simple logic gates along with an LED driver (see the...

New operational amplifiers optimized for high-performance audio and ultrasound applications combine extremely low total harmonic distortion plus noise (THD+N), -130 dB, with large output voltages on heavy, 600-? loads. One would think this might be the universal building block. In real life, it’s a bit more complex. For instance, op-amp input capacitance has a nonlinear behavior that’s a function of the input voltage. The associated input current will...

The proportional-control solenoids used in some industrial hydraulic systems are usually driven by microcontrollers or programmable logic controllers (PLCs). Such complex drivers typically require several different supply voltages for logic and control. (The purpose of proportional control is to move the solenoid plunger to an arbitrary position and leave it there.) A set-and-leave solenoid driver, however, should not require a costly PLC or the...

• Precision DC motor speed controller
• Voltage-To-Current Converter Works From A Single-Supply Rail
• Control circuit keeps dc motor running at constant speed
• Simple Circuit Maintains Water Level Between Two Preset Limits
• Ham Radio's Rejuvenation