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🤖Запрошуємо на відкриту лекцію "АІ: тренди та виклики" kpi чт, 04/23/2026 - 16:05

Circuits such as the design described here implement useful tools for a diversity of calibration and testing applications.

A two-wire loop current generator is a useful tool for the testing, calibration and commissioning of current-to-pressure (I/P) converters connected with control valves, actuators, etc. in process industries. Such product can also help calibrate the analog input modules of distributed control systems (DCSs) and programmable logic controllers (PLCs) by simulating process signals.

Wow the engineering world with your unique design: Design Ideas Submission Guide

In these and other applications, it is advantageous to generate a loop current which is linearly variable for precisely setting the desired current. A Design Idea published in EDN’s December 10, 2025 issue, although compact and otherwise excellent, does not support linearly variable current, since the output current relationship is Io=1.24/R1. R1 is adjusted to vary the output current, but since it is in the denominator of the equation, the resultant current variation is not linear.

Figure 1 describes a circuit where the variation of loop current is linear. Here, the loop current is directly proportional to the voltage set by potentiometer RV1. Moreover, this current can service a source or sink load up to 500 ohms without need for recalibration. These two requirements are essential for a loop current generator in process industries.

Figure 1 With this linearly adjustable two-wire current source, RV1 is adjusted to set the current, and either LOAD1 (source) or LOAD2 (sink) can be connected.

How does the circuit work? First connect a 24V DC supply, a DC ammeter and a load resistor—say, 200 ohms—at the source or sink side. In field applications, this portion is built into the I/P converter, DCS or PLC.

Two currents exist at pin 3 of U1A :

• I span=Vset/R5
• Through R4=(Io*R6)/(R4+R6)

The first current minus the second current = 0, as U1A is an operational amplifier.

Io is the loop current. Hence Vset/R5= (Io*R6)/(R4+R6). After rearranging, Io= (Vset/R5) * (1+R4/R6). Substituting the values, R4/R6= 99. Hence, Io= (Vset/R5)*100.

Thus, Io is directly proportional to Vset which is adjustable linearly by RV1. A multiturn potentiometer selected for RV1 will enable smooth and precise adjustment.

Other comments, in closing:

• U3 generates 5V DC.
• Q1 and U1A adjust the loop current Io proportional to Vset.
• R1 and Q2 set the current limit for Io at approximately 30 mA for safety reasons.
• The loop current is settable from 0.5 mA to 23.5 mA, which is sufficient for this application.
• For different current settings, select R3, R2 and R5 as per the equation given earlier for Io.
• And Q1 requires a heat sink.

Jayapal Ramalingam has over three decades of experience in designing electronics systems for power & process industries and is presently a freelance automation consultant.

Related Content

• Two-wire precision current source with wide current range
• A precision, voltage-compliant current source
• Precision current source

The post Linearly variable two-wire loop current generator appeared first on EDN.

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The traditional ASIC design model—focusing on relatively stable standards and well-defined functions—is now under pressure. That’s partly because AI workloads are highly diverse, compute-intensive, and tightly coupled to software behavior and system context. Consequently, ASICs, besides being application-specific, are now increasingly becoming system-specific.

Take the case of a custom chip for LLM inference, where the prefill and decode stages are now running on separate chips. So, there are two ASICs instead of one: the compute-intensive part of the application (prefill) and the memory-bandwidth-limited part of the application (decode). That shows how ASICs are increasingly becoming modular and disaggregated with cross-domain collaboration spanning architecture, packaging, and manufacturing.

Read the full article at EDN’s sister publication, EE Times.

The post The ASIC design remake in the AI era appeared first on EDN.

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The post The system architect’s sketchbook: GenZLens built in a dorm appeared first on EDN.

У КПІ відбувся традиційний турнір з волейболу імені Михайла Павловського kpi ср, 04/22/2026 - 17:02

Конференція «Чорнобильська катастрофа: медичні, екологічні та соціальні наслідки через 40 років» kpi ср, 04/22/2026 - 16:50

Аспірант КПІ на Міжнародному конкурсі з фізики kpi ср, 04/22/2026 - 16:44

Happy workbench Wednesday! I’ve been itching to post this since last Thursday haha. I’m Abacus of FooseyRhode and I specialize in repair of a specific type of computer part called an ASIC Hashboard, and those PCBs are what this setup is built around servicing. Honorable mentions at my desk that might catch some curiosity The Overhead Cable Trays. The rail mounted, Digital Microscope. The Heatgun Glory Hole. Soldering Iron suspended by pulleys. The Quad-table-top fans (Fan Deck). 1 and 2.) The overhead cable trays are super helpful for the obvious, but also for storing some accessories out of the way. My primary heatgun for example. With it up there, wrist strain from the heavy heatgun gun hose is practically eliminated. I also mounted my PC and digital microscope up there. Microscope benefits because table vibrations are gone, and computer is just there for cable management. 3.) See image 3. Looks crazy but it’s very necessary for my work. The PCB I work on are typically single layer PCB secured to a giant aluminum plate. A lone heatgun is not capable of achieving solder flow, and hot plates are extremely impractical for PCB like this. Thus, I apply heat from above, and below. Getting the damn thing mounted safely was the hardest part. I used a pneumatic vesa monitor mount, but backwards. I hammered the vesa mount into shape and secured it to a desk beam. Then I secured the opposite end of the mount to the heatgun. 4.) The pulleys just keep the soldering iron cable out of my way. Honestly, I’m just resolving a minor inconvenience for myself with this. 5.) My 3D printed Fan Deck! It’s four 120mm fans powered through a potentiometer so I can control the speed. It’s used primarily when I am diagnosing a board. The boards I work on use around 40-90 amps when operating, but for diagnostic, require only 10-20 amps to test properly. Point being, they heat up very rapidly, and heat affects my diagnostic. The Fan Deck is a means to cool boards down while simultaneously injecting power into them. submitted by /u/FooseyRhode [link] [comments]

CVD Equipment Corp (CVDE) of Central Islip, NY, USA (a designer and maker of chemical vapor deposition, thermal processing, physical vapor transport, gas and chemical delivery control systems, and other equipment and process solutions for developing and manufacturing materials and coatings) has announced the successful growth of single-crystal silicon carbide (SiC) boules grown on CVDE physical vapor transport (PVT) systems and characterized by Stony Brook University (SBU) in support of their new ‘onsemi Research Center for Wide Bandgap Materials’...

Simple math implemented in a (very) simple circuit. What’s not to like?

A very cool (also warm!) property of the base-emitter junction of (most) small signal BJTs is the ΔVbe temperature-sensing effect.  ΔVbe temperature measurement is aptly described and applied here by famed and forever remembered analog design guru Jim Williams (see page 7):

At room temperature, the Vbe junction diode shifts 59.16mV per decade of current. The temperature dependence of this constant is 0.33%/°C, or 198μV/°C. This ΔVbe versus current relationship holds, regardless of the Vbe diode’s absolute value.

Wow the engineering world with your unique design: Design Ideas Submission Guide

Rearranging Williams’ math, since 198uV=1V/5050, 198μV/°C per current decade works out to (the easier to remember…ha!) ΔVbe/°C = Log10(Current-ratio)/5050.  So, if we need any given ΔVbe/°C, the required

Current-ratio = 10^(5050 ΔVbe/°C).

For example, for ΔVbe/°C = 100uV, Current-ratio = 10^(5050 * 100uV) = 10^(0.5050) = 3.20

Of course, this trick also works for Fahrenheit, albeit with a different scale factor.  Since 1 °F = 5/9 of 1°C, for Fahrenheit the corresponding Current-ratio = 10^(9090 ΔVbe/°F).  Therefore, for the 100uV example, if ΔVbe/°F = 100uV, then Current-ratio = 10^(9090 * 100uV) = 10^(0.9090) = 8.11

Figure 1 shows this simple math implemented in a (very) simple circuit:

Figure 1 An ordinary BJT Q1 makes an accurate absolute temperature sensor in two different units (K and R).

Here’s how it works. Switch U1a applies alternating current ratio drive to sensor Q1 per Williams’ method.  The ratio is (approximately) Current-ratio = (1/R1 + 1/R2)/(1/R2) = (R2/R1 + 1) = 3.20 for measurement in units of Celsius (Kelvin) and = 8.11 for Fahrenheit (Rankine).  The “approximately” thing comes in because the resistor ratio needed to be fudged (slightly) to compensate for the few 10s of mV of varying difference between V+ and Q1’s Vbe and thus make the current ratios accurately equal to the calculated values.

The resulting 100uVpp per degree AC signal is synchronously rectified by U1b and filtered by C3 to become the 100uV per degree of absolute temperature DC output signal suitable for direct input to a DMM.  A ~5kHz clock signal for current switching and rectification is provided by U1c, with a little help from one side of U1a.

Note that, per Williams’ analysis of the ΔVbe effect, accuracy of temperature measurement relies only on the accuracy of the current ratio and therefore on only the precision of R1 and R2.  No other reference is required or relevant and any 2N3904 will do. 

The V+ supply, for example, can vary from 3 to 6 volts without affecting accuracy.  Passive output impedance is roughly 10k.  So, loading by a typical 10M DMM input won’t either.

Thanks, Jim!

Stephen Woodward‘s relationship with EDN’s DI column goes back quite a long way. Over 200 submissions have been accepted since his first contribution back in 1974.  They have included best Design Idea of the year in 1974 and 2001.

Related Content 

• Temperature compensation with a simple resistance temperature detector
• A temperature-compensated, calibration-free anti-log amplifier
• Thermopile sensors: A guide to non-contact temperature measurement

The post BJT is accurate sensor for absolute temperature in Kelvin and Rankine appeared first on EDN.

And wrote a blog post about it https://atomicsandwich.com/blog/breathing_apparatus submitted by /u/RonnieRehab [link] [comments]

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Квест "Святкуємо число Пі" в ДПМ Інформація КП ср, 04/22/2026 - 11:50

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