Amplifiers in use nowadays contain several stages
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Amplifiers in use nowadays contain several stages
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Content:
- Stem cells: past, present, and future
- What types of op-amps are available?
- What is an IC 741 Op Amp : Pin Diagram & Its Working
- Signal Acquisition Using Surface EMG and Circuit Design Considerations for Robotic Prosthesis
- Which ADC Architecture Is Right for Your Application?
- Subscribe to RSS
- Erbium-Doped Fiber Amplifiers (EDFA)
- Google AMP & SEO: Everything You Need to Know
- 6 Steps to Determining your Electrical Service Size
- 2sc5200 Pcb
Stem cells: past, present, and future
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts.
It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. I've always been told that ideally, op-amps have infinite input impedance. The is an old piece of junk, primarily used to teach basic electronics for cheap. I seem to remember reading somewhere that if every ever made were to be collected, there would be enough to give every person on earth 6 or 8 of them.
General Purpose - These op amps are not very fast, have bad non-ideal characteristics bias currents in the nanoamps , drift, have input impedances in the megaohms, and cost almost nothing. The falls in this category. FET Inputs - These are a bit faster, have significantly better non-ideal characteristics bias currents in the picoamps , drift very little, have extremely high input impedances gigaohms , but may cost a few dollars.
This is the type of op amp that can get its output within millivolts of the rails, but rail voltage is limited. It drifts very little, and has very low offsets.
Take a look at this article for more information. There are other op amps out there that can handle RF frequencys, or handle high output currents, but they don't really fall in these catergories. As you can see, each type of op amp has different non-ideal DC characteristics, and input impedance. How much current flows into the op amp inputs depends on the input impedance. For most modern op amps, these are very small currents, and can be considered negligible for the majority of applications.
Which type of op amp you use is a design consideration, factoring in speed, cost, temperature range, and any precision concerns. It's unfair to call the junk; it was something wonderful in its time.
Its close derivative, the LM, is still in volume production today, so obviously many people think it is the right tradeoff for their requirements. One significant advantage of the LM is its price. Often enough you just need a opamp without very stringent requirements. In general, it's a little easier to get the offset voltage down to a few mV with bipolars for the same chip area. There are also advantages in current drive capability and supply voltage range.
FETs of course have the really high input impedence. Nowadays these distinctions are more blurred. Nowadays, FET opamps are easier to make rail to rail for both input and output, but again compare the price of even the cheapest MCPxxxx with the old standby LM Also note the supply voltage range the LM can operate over. That's a tough trick for most of today's FET opamps. If you have a low impedance source, for the lowest noise of any available monolithic amplifier, you need to go to a bipolar amplifier such as the LT which has a white noise spectral density of 1.
If that's not good enough, a discrete design can do better. If you are doing audiophile audio processing, the best amplifier in the world is a Texas Instruments nee Burr-Brown bipolar part. It has a lot of input bias current, but very little distortion. The was designed in the mids, so almost 50 years ago. It was somewhat of an improvement over even earlier op-amps such as the uA , but it's pretty long in the tooth. Dual versions such as the venerable JRC have been used in audio applications for decades.
As Olin points out, the LM is similar the output stage has significant differences, in part to make it "single supply" , but costs only a penny or two per amplifier in quantity.
Aside from the LM, I don't think any other op-amp has achieved as wide use as the maybe some of the JFET amplifiers come close - the market is more balkanized, with many different choices for the designer, each with its own advantages and disadvantages. So for discrete systems, BJT is king.
For integrated systems on a chip MOS is king. This question's been answered several times over, but I feel like a mention should be made of JFET input stages.
These op amps typically use JFETs for the input differential amplifier stage, with most of the rest of the circuit being bipolar for the reasons others have given in their answers. The advantage of using FETs for the input stage is exactly as you say: they have much higher input impedance. If you look at the specs of various JFET-input op amps you'll see ones with input bias currents of less than ten picoamperes--and if you look at the ADL, for instance, it has an input bias of no more than 60 femtoamperes.
Standard bipolar op amps, for comparison, typically have input bias currents on the order of a few nanoamperes as in the OP07E , up to a microampere or two in some cases as in the famous LM Likewise, and for the same reasons, the input impedance of a JFET-input op amp will be five or six orders of magnitude greater than that of a bipolar op amp.
There's a tradeoff, though. JFET input op amps tend to have significantly greater input voltage noise. The bipolar OP07E mentioned above has low-frequency noise of less than 0. As with everything in life, there's no panacea that solves all your problems, there's no op amp that you can just be sure will meet your needs regardless of what they are.
If you need ultra-low bias current or very high input impedance, go with a JFET-input op amp. If you need low noise or low cost, go with a bipolar op amp. If you need something neither of those can supply, well, look into something more exotic. Chances are, you'll find it somewhere out there. Sign up to join this community. The best answers are voted up and rise to the top.
Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Ask Question. Asked 8 years, 10 months ago. Active 4 years ago. Viewed 28k times. Wouldn't using a BJT result in current flowing into the input pins? Nate Nate 1, 3 3 gold badges 13 13 silver badges 18 18 bronze badges.
Better to ask if and why some op-amps continue to be designed with BJT's today. Add a comment. Active Oldest Votes. Modern op amps fall into several categories. Take a look at this article for more information There are other op amps out there that can handle RF frequencys, or handle high output currents, but they don't really fall in these catergories. Anindo Ghosh Matt Young Matt Young Everything is a tradeoff. Olin Lathrop Olin Lathrop k 36 36 gold badges silver badges bronze badges.
I think "define your requirements" and "everything is a tradeoff" should be said more often in engineer education. Spehro Pefhany Spehro Pefhany k 12 12 gold badges silver badges bronze badges. Patrick Patrick 51 1 1 silver badge 1 1 bronze badge. Hearth Hearth 17k 2 2 gold badges 32 32 silver badges 81 81 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.
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What types of op-amps are available?
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What is an IC 741 Op Amp : Pin Diagram & Its Working
Classification based on the manufacturing process used Op-amps can be divided into two types according to the manufacturing process used: CMOS and bipolar. In contrast, bipolar processes withstand higher voltage than CMOS processes. The main cause of this noise is the crystalline disorder of silicon, which exists in abundance on the wafer surface. Therefore, CMOS op-amps are used for most applications nowadays. Classification based on the power supply type There are two types of op-amps: single power supply type and dual power supply type. Even single-supply op-amps can be used with dual power supplies as long as the difference between the minimum and maximum supply voltages does not exceed the differential input voltage range shown in the Absolute Maximum Ratings table. In this case, care should be exercised as to power supply noise since each power supply in the op-amp is not referenced to GND. However, the supply voltage range of typical op-amps is generally shifted toward the GND negative side, reducing the range of allowable positive supply voltage. Then, the common-mode input voltage can be restated as
Signal Acquisition Using Surface EMG and Circuit Design Considerations for Robotic Prosthesis
Electronic gadgets have become an integral part of our lives. They have made our lives more comfortable and convenient. From aviation to medical and healthcare industries, electronic gadgets have a wide range of applications in the modern world. In fact, the electronics revolution and the computer revolution go hand in hand.
Which ADC Architecture Is Right for Your Application?
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Several years ago, a standard electrical service size of amps provided enough electrical current to operate any devices the average home would use. Nowadays, many homes draw a lot more current than their service size allows for. Many homes now contain a large number of appliances, technology devices, and luxuries such as spas and pools that electrical contractors and homeowners could have never previously anticipated. Its rating is your overall home's electric service rating. Measure the diameter of the conduit that houses the service cable entry. This conduit houses the cable that comes from the electric company and enters the power meter box.
Erbium-Doped Fiber Amplifiers (EDFA)
It promises fast page speeds and additional visibility on Google result pages but demands submission to a stripped-down form of HTML. While there are glowing case studies, for many, the implementation was haphazard and the results confusing. AMP, formerly known as Accelerated Mobile Pages, are lightweight pages designed to give mobile users a lightning-fast, more engaging experience. Not too dissimilar from Facebook Instant Articles or Apple News, which also have the stated goal of making mobile content faster and easier to consume.
Google AMP & SEO: Everything You Need to Know
RELATED VIDEO: Stage Left Audio - \No electric guitar setup would be complete without a guitar amplifier. Nowadays, there are so many guitar amp makers selling their craft at many prices. These amps vary in complexity, size and quality. Various parts and components transistors, electronics, speakers etc. Also, there is a labor that needs to be paid. Most guitar amps are made up of 3 parts.
6 Steps to Determining your Electrical Service Size
COVID has governments at all levels operating in a context of radical uncertainty. The regional and local impact of the COVID crisis is highly heterogeneous, with significant implications for crisis management and policy responses. This paper takes an in-depth look at the territorial impact of the COVID crisis in its different dimensions: health, economic, social and fiscal. It has governments operating in a context of radical uncertainty, and faced with difficult trade-offs given the health, economic and social challenges it raises. Beyond the health and human tragedy of the coronavirus, it is now widely recognised that the pandemic triggered the most serious economic crisis since World War II.
2sc5200 Pcb
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