Новини світу мікро- та наноелектроніки

Intel Drops Four New Processor Families at CES

AAC - Птн, 01/15/2021 - 19:30
Intel has released more than 50 new processors at CES 2021, aimed at markets ranging from business to gaming.

Using an op amp as a comparator

EDN Network - Птн, 01/15/2021 - 19:03

In previous articles—Common op-amp circuits, Op amps do integration, and The practical op-amp differentiator is quite versatile—we looked at some classic op amp circuits. These circuits used negative feedback, which normally keeps the op amp operating in the linear region.

However, op amps can also be used as comparators, which causes them to operate non-linearly. The inputs are driven hard and the output voltage slams to the power supply rail. As we will see, this may not always be a good design approach.

Going non-linear

In a linear application, the ideal op-amp assumptions apply: infinite gain and bandwidth, zero output impedance, infinite input impedance and zero volts between the inputs. Op amps can also be used in a non-linear fashion, with some special care and handling.

A common configuration is just using the op amp open loop—without feedback—and letting its high gain produce comparator operation. Without negative feedback, the two inputs will not necessarily remain at the same voltage, so the fourth ideal op amp assumption is not valid.

Figure 1 shows an op amp configured in open loop. When VIN is greater than zero, the output voltage goes high and is limited somewhere around the positive supply voltage. When the input voltage goes negative, the op amp output swings negative, again limited near the negative supply voltage. Here, we assume the op amps are powered with the conventional positive and negative supply voltages.

Figure 1 The op amp is used as a comparator with zero threshold voltage.

The above comparator circuit operates around zero volts. Figure 2 adds a resistive divider to the circuit to set the voltage at the inverting input, providing a means to control the reference voltage for the comparator, VREF.

Figure 2 An op amp comparator with a resistive divider sets the threshold voltage.

Figure 3 shows another common design technique that adds hysteresis to the comparator. In this case, the input voltage drives the inverting input of the op amp and VREF connects to the noninverting input. The R1 R2 resistive divider produces VREF from output, VOUT. When VIN falls below VREF, the output voltage goes high, causing VREF to shift to a higher voltage.

Figure 3 Op amp comparator circuit adds hysteresis via positive feedback.

Similarly, when VIN transitions to be higher than VREF, VOUT changes to the maximum negative output voltage, pulling VREF lower. This hysteresis effect keeps any noise present on the input signal from reversing the comparator operation while transitioning past VREF.

The multi-vibrator circuit in Figure 4 uses the R1 R2 hysteresis circuit from Figure 3 plus an RC timing circuit to produce a square wave output. Actually, it’s not a comparator circuit; instead, it operates the op amp as a comparator to create the desired output waveform. Assume VOUT starts out as a high voltage such that it charges C via R3. The capacitor voltage will increase while being consistent with the time constant R3 C.

Figure 4 The multi-vibrator circuit adds an RC timing circuit to produce a square wave output.

When the capacitor voltage becomes larger than VREF, the output voltage will swing to the negative supply voltage. This causes the capacitor voltage to be driven negative, again consistent with the time constant R3 C. The R1 R2 divider provides some hysteresis on the non-inverting input so that the op amp transitions cleanly. See Reference 4 for the details on how the component values determine the multi-vibrator frequency.

But there are issues

There are many articles on the web about non-linear op amp circuits like these. However, when I checked the IC vendor websites, I noticed they strongly caution against using op amps as comparators [Reference 1 and Reference 2]. The main issues cited are:

  1. Some op amps have clamping diodes on the inputs which limit the maximum voltage between the two inputs. This can probably be handled with careful design or by choosing another op amp device.
  2. Comparator applications drive the op amp into saturation. Recovery from saturation can be slow and is generally not specified.
  3. The output voltage of most op amps can swing close to the positive and negative supply voltages. This may or may not be specified and it may not be well controlled.
  4. The switching time of an op amp tends to be slow as compared to a “real comparator” designed for that specific application.
  5. The output of the op amp is not usually set up to drive digital logic, so additional circuitry may be required to adapt it.

The main argument for using an op amp as a comparator occurs when there is a leftover amplifier in a multiple op-amp device. After all, it’s just sitting there, free of cost, waiting to be used. If you decide to pursue this path, then some careful study of the datasheet along with evaluation of the actual circuit performance is in order. Make sure that the op amp circuit has quite a bit of margin built-in.

These considerations of non-linear op amp operation may also help us understand some of the problems that can occur in linear applications. Are there situations when the output of the op amp gets driven to the rails? If so, how long will it take to recover? And does that matter in the performance of the circuit?

That’s why IC vendors recommend that you use a real comparator instead of an op amp. After all, a comparator is designed to be a comparator. It has specified switching characteristics and output drive, usually set up to drive logic devices. There are many economical devices to choose from.

Bob Witte is president of Signal Blue LLC, a technology consulting company.

References

  1. Op Amps used as Comparators—is it okay?” Bruce Trump, Texas Instruments, March 2012
  2. Using Op Amps as Comparators,” James Bryant, Analog Devices, Application Note AN-849, 2011
  3. Should I use an op amp as a comparator?” Janet Heath, Analog IC Tips, November 2016
  4. Op-amp Multivibrator,” Electronics Tutorials
  5. Handbook of Operational Amplifier Applications, Bruce Carter and Thomas R. Brown, Texas Instruments, Sept 2016
  6. Op Amps for Everyone, Ron Mancini, editor, August 2002

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ESP 32 ICONS AND ANIMATIONS

Open Electronics - Птн, 01/15/2021 - 18:45

In this project, I will provide examples for a house, thermometer and humidity sensor. Animations for a rain storm and cup anemometer is also included. To do it we need mainly an ESP32 board and an LCD display. More info

The post ESP 32 ICONS AND ANIMATIONS appeared first on Open Electronics. The author is Carlo Palumbo

GaN HEMT platform increases output power

EDN Network - Птн, 01/15/2021 - 18:43

GaN Systems offers an evaluation platform for its GaN enhancement-mode high-electron-mobility transistors (E-HEMTs) with half-bridge designs that boost output power by more than 30% without increasing size. This next-generation insulated metal substrate (IMS3) platform significantly improves heat transfer, resulting in lower thermal temperatures and higher power density.

The IMS3 offering comprises a motherboard and a choice of half-bridge power boards, available at two power levels of up to 3 kW and 6 kW. By applying high thermal conductivity, the IMS3 circuit boards demonstrate a 29% Rth case-to-heat sink thermal improvement.

The GS-EVB-HB-66508B-RN is a 650-V, 30-A GaN half-bridge and driver board. It furnishes two 650-V GaN E-HEMTs and all the required circuits to form a functional half-bridge power stage, including half-bridge gate drivers, isolated power supplies, and optional heat sink. Similarly outfitted, the GS-EVB-HB-66516T-RN is a 650-V, 60-A GaN half-bridge and driver board. These boards allow engineers to evaluate GaN E-mode performance in any half-bridge-based topology using GaN Systems’ universal motherboard.

3-kW GS-EVB-HB-66508B-RN product page 

6-kW GS-EVB-HB-66516T-RN product page 

GaN Systems 

Find more datasheets on products like this one at Datasheets.com, searchable by category, part #, description, manufacturer, and more.

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SemiLEDs’ quarterly revenue halves

Semiconductor today - Птн, 01/15/2021 - 18:27
For its fiscal first-quarter 2021 (ended 30 November 2020), LED chip and component maker SemiLEDs Corp of Hsinchu, Taiwan has reported revenue of $719,000, approximately halving from $1.4m last quarter and $1.563m a year ago...

AKHAN awarded additional patents in Taiwan and South Korea

Semiconductor today - Птн, 01/15/2021 - 16:52
AKHAN Semiconductor Inc of Gurnee, IL, USA – which was founded in 2013 and specializes in the fabrication and application of lab-grown, electronics-grade diamond as functional semiconductors – has been issued additional patents for invention by the Taiwan and Korean Intellectual Property Offices...

II-VI Inc ranked in industry awards at ODC 2020

Semiconductor today - Птн, 01/15/2021 - 12:11
II-VI Inc of Saxonburg, PA, USA, which supplies optoelectronic devices and micro-optics, says that it was twice recognized at a recent industry awards ceremony in China...

EPC’s eGaN FETs used in MPS’ 48V–6V digital DC-DC power conversion modules

Semiconductor today - Птн, 01/15/2021 - 11:58
Monolithic Power Systems Inc (MPS) of Kirkland, WA, USA has launched a family of 48V–6V digital DC-DC power modules for 48V data center solutions that use enhancement-mode gallium nitride on silicon (eGaN) power field-effect transistors (FETs) from Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA. The power modules target applications for high-density computing and data centers, artificial intelligence (AI), machine learning, and multi-user gaming...

Learn About the Thermal Characterization Parameters

AAC - Птн, 01/15/2021 - 06:31
In this article, we’ll discuss another group of thermal data, called thermal characterization parameters denoted by the Greek letter Psi (Ψ).

Two Up-and-Coming Companies Collaborate to Make Battery-Less IoT a Sustainable Reality

AAC - Птн, 01/15/2021 - 02:00
Current energy-harvesting designs have their limitations. e-peas and Sequans are coming up with what they call a "non-stop, zero-maintenance" solution.

The mysterious MS-DOS reboot

EDN Network - Чтв, 01/14/2021 - 22:26

Back in the early ‘90s, at the television station where I worked, we had a newsroom computer system that the reporters, anchors, and producers used to write and produce the newscasts. The system employed a pair of redundant servers and a newsroom full of PC workstations. The servers ran IBM’s OS/2 operating system, using the latest 90 MHz Pentium processors. (Ooh, that was fast!)

The workstations used 33 MHz 80386 CPUs running MS-DOS. No hard drives – just 3½” floppy disks. The floppy disks booted the computers to MS-DOS, and then ran a batch file that loaded the newsroom system’s executable program from the server. All the data, such as news stories and newscast rundowns, were stored on the server and everything connected over 10Base-T Ethernet running on a network hub (this was prior to network switches).

screen shot of a black and white MS-DOS command prompt

It all worked very well … that is, until one of our 11pm news anchors began reporting a problem.

Her workstation was occasionally and spontaneously rebooting, causing her to lose her unsaved work. We couldn’t find anything wrong with the workstation, so we replaced it. No good. We replaced her keyboard. Still no good. (No mouse change – there was no mouse; this was character mode MS-DOS.)

We replaced her network cable, changed to a different hub port, changed to a different homerun cable, and we even changed her monitor. Some of the swaps we did twice, but it still happened!

Finally, one day she wrote a very polite email to the news director, complaining that she had lost an hour’s work the previous night because her machine had rebooted, and she had to stay well past midnight rewriting her story. “If this keeps up, I’m afraid I’m going to have to ask for a new machine.” 

The news director called me and asked what was going on. I told him she apparently didn’t realize we had already given her two new machines. It didn’t seem to be a hardware problem. We decided to send one of my engineers to sit with her to see if he could figure out what was happening. I should have done that much earlier, as it took him less than five minutes to find the culprit.

The news anchor’s CPU tower was located on the floor under her desk, sitting on a short box. Back in those days, the CPU box had two buttons on the front – a power button and a reset button. The reset button connected directly to the NMI (non-maskable interrupt) pin on the microprocessor. Pressing the reset button produced an instantaneous hard reboot of the computer. 

She liked to sit with her legs crossed while she typed. While sitting with her our engineer looked down, and said, “How often do you figure you hit the reset button with the tip of your pointed high-heel shoe?”

And that, was that. 

Robert Yankowitz has been Chief Engineer at a television station in Boston, Massachusetts since 1999. Prior to that, he worked for 15 years at a station in an undisclosed city (to protect those with high-fashion footwear from embarrassment).

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Why a New 80 V Resistor-Equipped Transistor is Relevant for EV System Design

AAC - Чтв, 01/14/2021 - 20:00
With the hopes of future-proofing automotive designs, Nexperia has released an 80 V "RET." How are these components useful in EV design?

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