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Introduction to Using Zener Diodes As Voltage References

Jun 30, 2019

Zener (a.ka. avalanche or breakdown) diodes are p-n junction semiconductor devices designed to operate in the reverse breakdown region of their VI characteristic curve. By maintaining their reverse current within certain limits, the voltage drop across the diode will remain constant. If maintained in this mode of operation, the diode will act as a voltage reference.

Examine the spec sheet for a typically avalanche diode – Vz is the Zener voltage measured at a given test current Izt. The knee current Izk, is the minimum current through the device to maintain a constant Vz. Since the dynamic resistance at the knee of the of the response curve is high, if current through the device is below Izk, regulation will be poor. Izm is the maximum Zener current that can be passed without exceeding the maximum permissible power dissipation. Violate this and the device will turn into smoke before your eyes.

For operation as a voltage reference, a Zener Diodes must be reverse biased. When the reverse voltage is smaller than Vz only the normal diode reverse saturation current is allowed to flow. When forward biased it behaves like an ordinary silicon diode – a large forward current flows, and the forward diode voltage is typically 0.7 V. Avalanche diodes are available with maintaining voltages from several voltages to several hundreds volts and with power dissipation ratings up to 50 Watts.

The temperature sensitivity of a Zener Diodes (temperature coefficient) is given as a percentage change in reference voltage per centigrade degree change in diode temperature. This number is usually in the range of +/- 0.1 percent per deg C. The direction of the change is related to the mechanism of breakdown (avalanche multiplication versus Zener breakdown). Generally, if the reference voltage is above 6V the coefficient is positive, if below, negative. Some manufacturers have produced temperature compensated reference diodes by combining a positive temperature coefficient breakdown diode with a forward biased, negative temperature coefficient, silicon diode in a single package (i.e. the generic 1N829, a 6.2V reference diode with a temperature coefficient of +/- 0.0005 % per deg C over a range of -55 to +100 deg C). Rather than use a single larger diode it is often better to place multiple breakdown diodes in series when designing a high voltage reference. This combination allows higher voltage, higher power dissipation, lower temperature coefficient, and lower dynamic resistance (the reciprocal slope of the volt-amp curve in the operating region). Of course, this is a more costly solution than a single diode.


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Private Tuition Assists Parents Short of Time

Jun 28, 2019

This can be a difficult situation especially if the parents both work and don’t really have enough time to spend going over schoolwork with their child or if the parent does not understand the material that is being taught. Tutors can be a great solution to this problem because they have both the time and knowledge to help your child succeed in school.

There are many benefits that tutors can offer your child. The first, and most obvious thing that a child will get from having tutors is higher marks. Tutors have the ability to work with a child one on one and make sure that the material is clean and understood. This means that the child will be better prepared for the schoolwork and tests that are to come. The second thing that a child will get from having tutors is higher self-confidence. With higher grades, your child will feel a sense of accomplishment and he or she will know that anything is possible with hard work. Another thing that your child will benefit from with tutors is that he or she will be constantly providing support and advice to your child.

Hiring a private tutor before the crisis point may prevent it altogether
There are two very simple reasons for this. First, effective education takes time. Second, education is most effective when it develops organically out of a supportive, focused learning relationship. Of course a good tutoring situation will provide a framework for that sort of relationship, but there is only so far the relationship will be able to develop if time is short.

If difficulties in school, personal or academic, are a factor, long-term thinking is especially important since confidence and self-esteem hang in the balance with results. If a difficult situation is allowed to drag on, the impacts on a student’s performance and psyche can go very deep, making the process of improvement much more complicated later.

With the luxury of time, a good tutor has the opportunity to make use of a variety of resources and approaches to tailor-make his or her teaching to the needs and personality of the student. This makes the teaching much more productive and the learning much more enjoyable, which is of course the magic formula for academic success.

Planning as far ahead as possible is critical when considering private tuition
For all of these reasons, parents should take the longest view possible when considering private tuition. A few weeks-or even a few months-before exams can’t hurt in a desperate situation. But the results of a handful of weeks or months will naturally fall short of those of a well-structured learning programme, honed and refined over time, which allows a student to prepare fully and confidently.

Families considering private tuition should consider getting it in place at least a year in advance, ideally more, if at all possible. It should begin long before exams loom, or, in the case of challenges arising from school, as soon as the troubling situation is clearly identified. To wait is to sacrifice day by day a student’s potential performance, sense of well-being, or, worst of all, both. At the risk of sounding like a public-service announcement, when it comes to private tutoring, action is far more effective than reaction, and prevention far more efficient than cure.

In addition to general subjects, Tuition agency can help your child prepare for upcoming exams. This includes any tests that will be given in class as well as any entrance exams that must be taken before the child can apply to college.

Whatever you needs, there are Tuition agency available. The Internet is a great place to start your search for qualified tutors for your child. You will want to make sure the tutors that you choose have the qualifications and knowledge to be able to help your child. Make sure to read online reviews for both tutors and sites that offer tutoring. With the right help your child can succeed in school, so choose the help that is available carefully.

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How to Select Baby Car Seats – 4 Factors You Should Know

Jun 28, 2019

If you plan to travel a lot with your baby, you should consider adding a baby car seat to the list of equipment you definitely need to have. Having a car seat for your baby is the only way you are going to keep your baby secure as you drive your car. Not only is it a requirement by law but it is also an investment in the safety of your child.

Typically, car seats are miniature seats that snugly secure your baby as you travel about in your car. The seats are firmly and safely attached to free seats in the vehicle. There are hundreds if not thousands of car seat designs you can select.

When looking for a baby car seat you should consider the following:

1) Comfort:

Some car seats are roughly made and it will show in the craftsmanship. Rough edges and tough padding will make travel uncomfortable for your child. It would be best to find seats with a comfortable build. Padding that is soft yet firm is an added bonus. Make sure there are no sharp edges around and within the seat area. This could cause a bruising or gouging hazard so keep all those edges blunt.

You want to consider designs that support your baby’s back and neck. Babies can’t hold their neck up, so they will need a seat that will make sure that his or her head is kept in a comfortable position. This should be all the more important considering how babies love to wiggle and squirm.

2) Quality:

Check the seat for any irregularities in its design. Look for areas that are susceptible to breaking and wearing out. The baby seat should be lightweight and easy to manage, yet tough enough to ensure the safety of your child. Remember that the most important aspect here is safety. So keep a parent’s eye out for any design flaws that could contribute to such.

When attached to a car seat, the baby’s harness shouldn’t wobble to and fro. It should be stable and secure to ensure that your baby does not get rocked violently.

Stay away from second-hand car seats as they could already be damaged or worn out. This will compromise your child’s safety, so it is best to refrain from even considering such equipment.

3) Complexity:

Does the harness take too much time to secure? If so you might want to consider other models that allow for a more straightforward approach to securing and removing your baby from the harness. Of course, even if this is the case do not forget that the most important aspect of any car seat is its safety. If you were to choose between a harness that was a little complex but safe, and one that was easy to secure but comes off on its own, go for the former.

However, you will still have to worry about how hard it is to detach such a harness. Go for baby car seats that allow for maximum safety and easiest securing of children. Also try reading the manual for each baby car seat to find out the guidelines and functionality each one offers. This will give a better idea on comparing each baby car seat by make and function.

4) Size:

The size of the Baby car seat Singapore will generally depend on how large your baby is. Make sure, however, that the harness goes over the pelvis of your baby and not over his or her stomach. If the harness goes over the stomach instead, you should consider getting a different baby seat. The baby’s hands and feet should also fit snugly within the car seat to avoid getting injuries to these parts. If the seat is too big for the child, it will show since you will notice that he or she does not fit the seat snugly.

Choosing the right car seat for your baby is important in assuring a safe and comfortable ride for the both of you. Sometimes, the choice of Baby car seat Singapore you make depends on the needs of your baby – size, comfort, and durability. Use the guide above to get a better understanding and idea of how to choose the right seat for your baby.

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Oil Based Facial Cleansers – Are They For You?

Jun 26, 2019

If you are combating oily skin, the last thing you may want to hear is someone recommending you wash your face with oil! But guess what? Oil-based facial cleansers do exist, and even more  so, people are starting to flock towards using them.

Still shocked by the thought of rubbing oil onto your face? Proponents for oil-based facial cleansers use the logic from the chemical world that “like attracts like.” This sort of reflects the old adage, “Fight fire with fire.” Anyway, back in terms of facial care. In order remove the oils that are “gunking” up your face, you need to dissolve them. Oils will naturally dissolve oils because they have the same chemical structure and are able to bind to one another. Oils are actually good at dissolving anything, including makeup. So you wash away everything in one fell swoop.

If you are still not a believer, then consider another reason to use oil-based skin cleansers. A lot of makeup is hard to remove, especially waterproof mascara. Using oil-based cleansers can make removing makeup a snap. Basically, the lipids in the oils surround and breakup the hard-to-remove makeup. So if you’re tired of yanking out eyelashes from trying to remove your mascara, maybe it is worthwhile to try oil-based cleansers.

Oil-based facial cleansers can contain castor, olive, jojoba, emu, safflower, sunflower, avocado or almond oil, just to name a few! Sounds like an organic symphony, but do not assume all oil-based facial cleansers are organic. Most will contain chemical ingredients, if only to stabilize and increase shelf-life of the cleansers. The addition of propylene glycol also helps the viscosity and smooth flow of the cleanser.

Not all oil-based cleansers are liquids. Some Best Facial Cleanser are oils mixed with water, emulsifiers and thickeners. Have you heard of “cold creams?” Those are actually oil based; look at the ingredients and you will see mineral oil.

Now, mineral oil itself has been part of a long-standing debate. Health conscious people claim mineral oil, which is derived from petroleum, is not a substance that belongs anywhere near the human body, period. While it is true that inhaling mineral oil is dangerous, rest assured that mineral oil that is used in facial products has been refined and highly purified. It has passed safety testing for use in cosmetics. To date, there have been no scientific studies that linked cosmetic grade (highly purified) mineral oils to cancer. However, you should do your own research and read reviews on some of the common cold creams to decide if you want to give them a try.

If you are serious about testing oil-based cleansers, then how about following the “oil cleansing method” completely? This method involves using nothing but oil to clean your face! Mix together the oils, then spread it over your face. Wait a few minutes, then apply a warm washcloth over your face. The point of this step is to steam open pores to allow the oils to work their ways in for a deep cleanse. Lastly, rinse or wipe away the oils with a clean towel.

Fight oil with oil! There is only one way to find out if this method can work for you, and that is to give oil-based Best Facial Cleanser a try. If you need to work up the courage, do an internet search. You’ll find lots of fans and believers in the oil cleansing method. Maybe it’ll work for you, too.

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A Brief Overview Of Industrial Laser Diodes

Jun 26, 2019

Laser diodes have many uses in today’s world, from military applications to telecommunications, meteorology and medicine. There are several common modes of operation and a wide variety of structures to suit proposed industrial uses.

Operation of Laser Diodes

A laser diode is similar to a light-emitting diode (LED) in that it has as its active medium a semiconductor. The most usual type of diode is found at a p-n junction (the boundary between p-type and n-type semiconductors) that is created by a process called doping. These junctions are then powered by injected electric current and are called injection laser diodes to differentiate them from optically pumped laser diodes.

Many diodes emit in continuous wave (cw) mode from anywhere from several watts down to just milliwatts of power. These industrial diodes lack the ability to be overdriven and even small periods of exceeding the maximum power can cause damage to laser resonators and effectively shut down the laser. For industrial applications that require a lot of peak power usage time, pulsed laser diodes are able to be overdriven effectively and easily for short time periods. To achieve this, short pulses are followed by pauses, keeping the pulse lengths in the 200ns range. These pulses of light are generated by laser currents that lessen inductive loss through the use of fast switching transistors and very short electrical connections.

Laser Structures Over the Years

Laser diode technology has changed rapidly from the early 60s, when it was demonstrated at the IBM T.J. Watson Research Center. Since then, we have seen diodes move from liquid phase epitaxy (LPE), or layering of crystals, to molecular beam epitaxy and organometallic chemical vapor deposition in the 1970s. These forms have been added to and expanded with the addition of Vertical Extended Cavity Surface Emitting Lasers (VECSELs), Vertical Cavity Surface Emitting Lasers (VSELs), external cavity Switching Diodes and others, including subcategories.

Common Industrial Uses

Some of the smaller varieties of Switching Diodes are used in laser printers, bar code scanners, laser pointers and CD planners. But the larger diodes are used in many important defense applications, such as the pulsed laser rangefinders in military tanks and directed energy strike systems that produce powerful light to destroy land mines, rockets, mortar rounds and other ordinances. The medical community benefits through the use of this technology through cosmetic applications such as Intense Pulsed Light (IPL) for hair, age spot, and wrinkle removal, other lasers for soft tissue surgery, and even in dentistry for procedures as diverse as cavity removal and tooth whitening. Vertical extended cavity surface emitting lasers (VECSELs) are important for big screen televisions and other commercial uses. Other various applications for laser diodes include welding and cutting of metals and other industrial materials, fiber optics for telecommunications systems, laser levels for surveying, and the taking of accurate 3D measurements.

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Tantalum – Where Would Our World Be Without This Rare Technical Metal?

Jun 24, 2019

Tantalum a Rare Technical / Strategic Metal named after a Greek mythological figure, Tantalus. Tantalus stole from the temple of Zeus and was punished with, ¨Eternal Torment¨, for his wrong doings. Anders Gustaf Ekeberg, who discovered Tantalum in 1801 in Finland, named the very stable metal this because it must, ¨Languish in pain and not quench its thirst¨, as did Tantalus in the underworld.

The modern world would languish in pain if Tantalum were absent. It was used to light up entire cities in the past as Tantalum the element was used in the manufacturing of filaments for light bulbs before Tungsten took over its application. Could you imagine if your cell phone was still the, ¨Brick Phone¨, of 80´s fame? What if you had to have a truck to carry your personal computer around with you? Could you imagine a 60¨ Inch CRT TV? Do you like that portable GPS system? How about those large hearing aids?

Today, this Rare Technical / Strategic metal is used in many applications. In fact our modern 21st Century society would not be the same without Tantalum. Do you remember the 1970´s? Tantalum capacitors are small, powerful and suitable for high-frequency ranges. Every electronic device around you uses Tantalum capacitors. Tantalum has also made it possible for long term medical implants because it is non-toxic and does not react with body fluids. This rare metal is also used as a high temperature alloy in aircraft turbines because of its high melting point.

Currently the amount of Tantalum mined is approximately 1,160 tons annually. Tantalum Capacitors alone use up 551 tons of the annual production. By the year 2030, the amount needed for capacitors will rise to an estimated 1410 tons. Do you see what I see? The future needs of Tantalum far outweigh the current amount mined. A few years ago Tantalum became known as a conflict metal because of its illegal mining in the Congo. Currently most of its production is coming out of Australia with Brazil and Canada a distant second and third.

For those of us who like to put our money on commodities that will rise, I think Tantalum Capacitors is a grand choice. Also Tantalum is not traded on the commodities exchange so buying it is no different than buying a pile of dirt. No options trading on this metal! Buy and hold, just like my Father taught me.


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Metal Oxide Semiconductor Field-Effect Transistors

Jun 20, 2019

Metal oxide semiconductor field-effect transistors (MOSFETs) are incredibly popular transistors that in some ways resemble JFETs. For instance, when a small voltage is applied at its gate lead, the current flow through its drain-source channel is altered. However, unlike JFETS, MOSFETs have larger gate lead input impedances (≥1014 Ω, as compared with 109 Ω for JFETs), which means that they draw almost no gate current whatsoever. This increased input impedance is made possible by placing a metal oxide insulator between the gate-drain/source channel. There is a price to pay for this increased amount of input impedance, which amounts to a very low gate-to channel capacitance (a few pF), through the gate and destroy the MOSFET. (Some MOSFETs are designed with safeguards against this breakdown-but not all.) Both enhancement-type and depletion-type MOSFETs come in either n-channel or p-channel forms.

MOSFETs are perhaps the most popular transistors used today; they draw very little input current, are easy to make (require few ingredients), can be made extremely small, and consume very little power. In terms of applications, MOSFETs are used in ultrahigh input impedance amplifier circuits, voltage-controlled “resistor” circuits, switching circuits, and found with large-scale integrated digital ICs. Like JFETs, MOSFETs have small transconductance values when compared with bipolar transistors. In terms of amplifier applications, this can lead to decreased gain values. For this reason, you will rarely see MOSFETs in simple amplifier circuits, unless there is a need for ultrahigh input impedance and low input current features.

OHMIC REGION MOSFET is just beginning to resist. In this region, the MOSFET behaves like a resistor.

ACTIVE REGION MOSFET is most strongly influenced by gate-source voltage (VGS) but hardly at all influenced by drain-source voltage (VDS).

CUTOFF VOLTAGE (VGS, off) Often referred to as the pinch-off voltage (Vp). Represents the particular gate-source voltage that causes the MOSFET to block most all drain-source current flow.

BREAKDOWN VOLTAGE (BVDS) The drain source voltage (VDS) that causes current to “break through” MOSFET’s resistive channel.

DRAIN CURRENT FOR ZERO BIAS (IDSS) Represents the drain current when gate source voltage is zero volts (or when gate is shorted to source).

TRANSCONDUCTANCE (gm) Represents the rate of change in the drain current with change in gate-source voltage when drain-source voltage is fixed for a particular VDS. It is analogous to the transconductance (I/Rtr) for bipolar

MOSFET Drivers may come with a fourth lead, called the body terminal. This terminal forms a diode junction with the drain-source channel. It must be held at a non conducting voltage [say, to the source or to a point in a circuit that is more negative than the source (n-channel devices) or more positive than the source (p-channel devices)]. If the base is taken away from the source (for enhancement-type MOSFETs) and set to a different voltage than that of the source, the effect shifts the threshold voltage VGS,th by an amount equal to 1⁄2VBS 1/2 in the direction that tends to decrease drain current for a given VGS. Some instances when shifting the threshold voltage becomes important are when leakage effects, capacitance effects, and signal polarities must be counterbalanced. The body terminal of a MOSFET Drivers is often used to determine the operating point of a MOSFET by applying an incremental ac signal to its gate.

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Op Amp Inverting Amplifier- Operational Amplifier Circuit

Jun 18, 2019

The op amp inverting amplifier circuit is very easy to design and can be implemented with a very limited number of additional components.

In its simplest form the op amp inverting amplifier only requires the use of two additional resistors.

This the inverting amplifier can also be used as a virtual earth mixer, but it is also worth noting that the input impedance of this op amp circuit is not as high as the inverting format.

Op amp inverting amplifier circuit

The basic diagram for the inverting Op Amps circuit is quite straightforward and only needs a few components beyond the operational amplifier integrated circuit itself.

The circuit consists of a resistor from the input terminal to the inverting input of the circuit, and another resistor connected from the output to the inverting input of the op-amp. The non inverting input is connected to ground.

Inverting amplifier gain

One of the main features of the inverting amplifier circuit is the overall gain that it produces. This is quite easy to calculate. The voltage gain, Av, is actually the output voltage (Vout) divided by the input voltage (Vin), i.e. it is the number of times the output voltage is larger than the input voltage.

It is also easy to determine the equation for the voltage gain. As the input to the op-amp draws no current this means that the current flowing in the resistors R1 and R2 is the same.

Op amp inverting amplifier design hints and tips

The op amp inverting amplifier is very easy to design, but as with any design there are a few hints and tips that can be of use.

  • Don’t make R2 too high: Although the input impedance of op amps is high, it is always best to ensure that the value of R2 is not chosen to be too high otherwise other circuit effects may load it and the value of gain may not be what is expected. It is often wise to keep the value of R2 below 100kΩ as a rough rule of thumb.
  • Don’t make R1 too low: It is also wise not to make the value of R1 too low in the op amp inverting amplifier. Remember that it determines the input resistance of the inverting amplifier circuit. If AC coupling the input circuit, the value of the series coupling capacitor will need to be chosen so that its reactance is sufficiently low at the lowest frequencies needed. Lowering the value of R1 increases the value of capacitor required. Also making R1 too low increases the loading on the previous stage.
  • Remember bandwidth: Although Op Amps have a high value of gain, this starts to fall at increasing frequencies. Even with feedback in the inverting amplifier, the gain bandwidth product needs to be considered. Don’t try to get too much gain out of a single stage, otherwise the frequency response may suffer.
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Face Lift and Eye Lid Surgery: A Career Investment

Jun 16, 2019

Recently an article crossed my desk describing how a 45-50 year old male attorney began hearing remarks from his colleagues that he looked tired. Even though his suit was meticulous, starched collar and silk tie – he felt great but his facial appearance had begun to wane.

Consider this: A tall, shapely woman confidently dressed in form-fitting leotards and tights working out in her favorite spa. From the back view she looks like a 20 something – nothing jiggles – her waist, tummy, and thighs all in proportion. But as she turns, you see the tired, stressed out face of a definitely 40ish or older woman desperately trying to hold on to her youth.

This scenario represents the graying of the Baby Boomers; they see aging faces developing right before their eyes and they feel helpless thinking that they, too, may have to succumb to a surgical procedure to maintain the look of health and youthfulness as a career investment.

Will they need a mini-lift? Eye lid surgery? Liposuction on their chin and neck? Not so long ago, “nips and tucks” were quiet affairs and only available to celebrities and business moguls’ wives; today plastic surgery is becoming mainstream as more and more financing options become available. Business execs, sales people, secretaries, practically every one over the age of 20 realize that their facial appearance speaks volumes about themselves: Furrowed brows: angry and explosive. Down Turned Mouth Corners: looks sad, maybe depressed Double Chin & Jowls: Looks old – old ideas.

Surgical procedures are risky. There is not one procedure performed under the guise of plastic surgery that is risk-free. Not only does a patient risk infection from an invasive procedure; scarring and loss of sensation are also a concern. There have been cases where people have suffered brain damage from anesthesia and some have died.

At what point is seeking improvement detrimental? With so many procedures available, one has to ask if the medical community has slipped into an “assembly line” status.

These very serious surgeries may disfigure one’s face and body as witnessed in many recent television shows portraying botched procedures. Noses, breasts, chins implants, liposuction nightmares and faces that look distorted cost someone a lot of cash and emotional anguish.

Imagine, paying hard earned money for a look that you may not embrace and maybe paying more to correct something that may need to be tweaked. Once tissue has been cut and sutured, it is never the same. Susan Sarandon, in a rare moment of candor, expressed succinctly to Ellen DeGeneres, “I’m scared of plastic surgery. You’re somewhere between a burn victim and a female impersonator, and then there’s a kind of an Asian thing going on.”

What if the procedure goes smoothly; there are no problems and the patient is satisfied with the new look? How long will this investment last? Most facial plastic surgery procedures, especially injections, will have to be repeated again and again. Imagine facing another surgery – anesthesia and more cutting can eventually disfigure a face. The average surgical procedure is $20,000. Multiple expenditures can quickly add up to staggering amounts.

More and more people are opting for non-surgical methods of facial rejuvenation; in fact, just as isometric and resistance type exercise works to reshape the body, facial exercise can significantly reverse the look of aging in every face. Here’s how: As we age, muscles in the face slowly relax and as they relax your skin begins to follow the downward motion. Jowls and little pouches form on the jaw line, the eyelids begin to fold and a visible line develops in your cheeks between your nose and mouth.

Unlike the major muscles in the body, the facial muscles are small; in some areas they weave over and under each other, and they attach at only one end to a bone. This means they cannot contract without an artificial anchor – in our arms and legs, we have joints that act as anchors so that we can tense our muscles with contractions. In order to contract the facial muscles so they tone, tighten and lift they must be held or anchored. This action provides increased circulation and oxygenation. This means that contortions – movements without resistance – will not contour the face and neck. Resistance exercise lifts your face from the inside out.

Using double eyelid surgery will reshape and lift your face. These exercises create stronger, more resilient muscles and facial skin will tighten preventing further sagging. The jowls will lift, eyes will open and look vibrant and the “apples” in your cheeks will return. With double eyelid surgery, you can look younger and people will recognize you even if you haven’t seen them in twenty years because you will still look like you.

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Fundamentals of Semiconductor C-V Measurements

Jun 16, 2019

Capacitance-voltage (C-V) testing is widely used to determine semiconductor parameters, particularly in MOSCAP and mosfets structures. However, other types of semiconductor devices and technologies can also be characterized with C-V measurements, including bipolar junction transistors (BJTs), JFETs, III-V compound devices, photovoltaic cells, MEMs devices, organic TFT displays, photodiodes, carbon nanotubes (CNTs), and many others.

The fundamental nature of these measurements makes them useful in a wide range of applications and disciplines. They are used in the research labs of universities and semiconductor manufacturers to evaluate new materials, processes, devices, and circuits. C-V measurements are extremely important to product and yield enhancement engineers, who are responsible for improving processes and device performance. Reliability engineers use these measurements to qualify material suppliers, monitor process parameters, and analyze failure mechanisms.

With appropriate methodologies, instrumentation, and software, a multitude of semiconductor device and material parameters can be derived. This information is used all along the production chain beginning with evaluation of epitaxially grown crystals, including parameters such as average doping concentration, doping profiles, and carrier lifetimes. In wafer processes, C-V measurements can reveal oxide thickness, oxide charges, mobile ions (contamination), and interface trap density. These measurements continue to be used after other process steps, such as lithography, etching, cleaning, dielectric and polysilicon depositions, and metallization. After devices are fully fabricated on the wafer, C-V is used to characterize threshold voltages and other parameters during reliability and basic device testing and to model the performance of these devices.

The instrumentation software should include ready-to-run test routines that do not require user programming. These should be available for the most widely used device technologies and test regimens, which were mentioned in the first three paragraphs of this article. Some researchers may also be interested in less common tests, such as performing both a C V and C f sweep on a Metal Insulator Metal (MIM) capacitor, measuring small interconnect capacitance on a wafer, or doing a C V sweep on a two-terminal nanowire device. The parameter extractions should be easily obtained, with automated curve plotting.

Often, engineers and researchers are expected to perform C-V measurements with little experience and training on the instrumentation. A mosfets with an intuitive user interface and easy-to-use features makes this practical. That includes simple test setup, sequence control, and data analysis. Otherwise, the user spends more time learning the system than collecting and using the data.


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