The output voltage of difference amplifier gets affected because of the mismatch resistors It is basically a differential amplifier, that performs amplification of difference of input signal. Whether a difference amplifier is "less" or "more" expensive depends also on how well it solves the problem compared to the alternatives. Why use difference amplifiers over instrumentation amplifiers? Back to basics introduction to the differential amplifier, aka the diff-pair, long-tailed pair, emitter coupled pair, etc. For more information on cookies, please read our, Wireless Sensor Networks Reference Library, Instrumentation Amplifiers requires membership for participation - click to join, Switch The differential amplifier can be built with a single operational amplifier. The parts make up a system. How does it compensate for this? & Reliability, Sales & Differential amplifier vs Instrumentation amplifier. Interested in the latest news and articles about ADI products, design tools, training and R4 has an additinal 200k ohm parallel impedance, while R2 additional 100k ohm, so this is the unbalance. @Janka but after the initial buffer isnt the input impedance to the differential amplifier R2+R3 so the input signal would be changed anyway? I'm trying to understand what is the advantage of using a difference amplifier as opposed to an instrumentation amplifier. Differential amplifiers are specifically designed to amplify the difference between 2 input signals. to mobile view, Analog But, on the other hand, a differential amplifier has both a differential input and a differential output: it drives two output pins in anti phase, centered around a common mode reference voltage that it accepts as an input (or generates internally). share | improve this question | follow | asked Aug 7 '19 at 3:52. 1 Corinthians 3:15 What does "escaping through the flames" convey? AD521 : Integrated Circuit Precision Instrumentation Amplifier (AA Enabled) AD524S : Precision Instrumentation Amplifier (AA Enabled) AD620/AD : Low Power High-Accuracy Instrumentation Amplifier. An instrumentation amplifier is a special kind of differential amplifier. When you say they compensate the impedance mismatch what do you mean? Room, Quality The InAmp, based around the differential amp, gets around this problem. Definition: A special type of amplifier that is used to amplify signals of extremely low-level is known as Instrumentation Amplifier. A non-inverting amplifier is connected to each of the input of the Differential Amplifier. I understand some advantages but I am still unsure of what the main reason is for why we use instrumentation amps for small differential signals. As in for a standard differential amplifier the input impedance is low and so this may cause differences for the input signals. us, Investor How many dimensions does a neural network have? 9 year old is breaking the rules, and not understanding consequences. An instrumentation amplifier (INA) is a very special type of differential input amplifier; its primary focus is to provide differential gain and high common-mode rejection. of what an instrumentation amplifier is, how it operates, and how and where to use it. They may include specially matched resistors to help optimize this function. Instrumentation Amplifier. But in all cases, advantages and disadvantages can only be determined as they apply to a given application. And of course you'd have to characterize the performance of this custom design yourself. Why is an Instrumentation Amplifier Used Over a Standard Differential Amplifier? The term instrumentation amplifier is often misused, referring to the application rather than the architecture of the device. Sometimes low price is the best advantage - say you're designing some simple toy that will work just fine with the most basic, low-spec op-amp you can find. However with the buffer this solves this stages side but for the differential amplifier side wouldnt it be the same as just one differential amplifier? The addition of input buffer stages makes it easy to match (impedance matching) the amplifier with the preceding stage. While those are the extremes, it's all a continuum. This is close to the Ideal Instrumentation Amp, High Z and Excellent CMRR. They do. The asymetric impedance of OA is compensated by buffers (IA first stage buffers). This Wheatsone bridge won't suffer too much about asymetry and input resistance. You presume that in-amps and diff-amps are typically alternative choices and thus could be compared "apples to apples": not usually. amp. Fig. It cancels out any signals that have the same potential on both the inputs. The instrumentation amplifier also has some useful features like low offset voltage, high … Since without these amplifiers, the second stage is just a normal differential amplifier Differential "Instrumentation" Amplifier with one op amp: Find V+ Write KCL for the V- node, assuming V- = V+ rearrange, solve for Vout substitute in the expression for V+ group the V2 terms together, perform more algebra, keep going ... cancel the R1+R2 terms, therefore, CAN ALSO SOLVE BY SUPERPOSITION: FIRST V1 THEN V2 APPLIED . Instrumentation amplifier is a kind of differential amplifier with additional input buffer stages. But, say, if you want to shift the output level of the in-amp, you'll quickly find that most "buffered" voltage-output multichannel "trim" DACs (8-12 bits) either have too high DC output impedance (5-40Ohm are quite typical) and thus degrade the in-amp's CMRR, or they have excellent output impedance (<0.1Ohm) but very high noise (>100uV p-p, that's two LSBs in a 16-bit A/D system with a 5V input span). Instrumentation amplifiers are precision, integrated operational amplifiers that have differential input and single-ended or differential output. The in-amps are w In addition, several dif-ferent categories of instrumentation amplifiers are addressed in this guide. Specifications subject to change without notice. AD620A/AD : Low Power High-Accuracy Instrumentation Amplifier. There aren't all that many dual in-amps! Inconsistent Gain with Instrumentation Amplifier. an instrumentation amplifier or difference amplifier seems like an obvious approach for AC coupling, but it has prob-lems. F Information furnished by Analog Devices is believed to be accurate and reliable. The instrumentation amplifier is one type of differential amplifier; Instrumentation amplifier can be built with three operational amplifiers. The offset drift is attributable to temperature-dependent voltage outputs. Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. The IA buffer first and then feeds the difference amp, thus the current fed to the inverting input is higher compared to the non-inverting, voltages are not affected, this is this compensation or impedance match with other words. delivered monthly or quarterly to your inbox. Why don't INA's have differential outputs? Many of them have high impedance inputs. For example, the differential signal that I have is very small and comes from a Wheatstone bridge configuration. IN-AMPS vs. OP AMPS: WHAT ARE THE DIFFERENCES? The so-called instrumentation amplifier builds on the last version of the differential amplifier to give us that capability: Understanding the Instrumentation Amplifier Circuit. These buffer amplifiers reduce the factor of impedance matching and making the amplifiers especially appropriate for measuring purposes. The buffers have low output impedance and they compensate the impedance mismatch of the difference amp inputs. Introduction This three-part article about instrumentation amplifiers (IAs) discusses common-mode versus differential-mode signaling, basic operation of the traditional 3-op amp topology, and how to interpret and simulate the V CM vs. V OUT plot.. Triple Op-Amp Instrumentation Amplifier Advantages and Disadvantages of Differential Amplifier as Instrumentation Amplifier This intimidating circuit is constructed from a buffered differential amplifier stage with three new resistors linking the two buffer circuits together. How do I provide exposition on a magic system when no character has an objective or complete understanding of it? Analog Devices instrumentation amplifiers (in-amps) are precision gain blocks that have a differential input and an output that may be differential or single-ended with respect to a reference terminal. They are called difference amplifiers :) You seem to be fixated on redefining what an INA is. Instrumentation Amplifier which is abbreviated as In-Amp comes under the classification of differential amplifier that is constructed of input buffered amplifiers. An InAmp consists of a differential amp with a buffer amplifier on each input. When measuring signals from high impedance transducers or wheatsone bridges, the current to the apmlifier shall be very low, in ideal case zero, so it doesn't affect the source itself. I wouldn't think there's that much difference though. It may be a cheaper part that is a poorer match to the application and requires more expensive choice of other system components - or vice versa, it may be a much better match that makes everything else much easier. Should I hold back some ideas for after my PhD? @Student The wheatstone bridge can be connected to the difference amp directly as long the bridge impedance is very low compared to the input imedance of the diff. The differential amp has impedance on inverting input equal to R2, while the non-inverting has R2+R3. The drive strength of the first stage outputs is much higher than the drive strength of your external source, so at the same impedance of the second stage, the error due to the current limitation is much smaller. This won't happen with an instrumentation amp. Why is a Instrumentation Amplifier Necessary for A Wheatstone Bridge (small signal circuits), Not understanding how the gain works in the 1st stage of an instrumentation amplifier. Since without these amplifiers, the second stage is just a normal differential amplifier Another question is when do we use just a single differential amplifier (why do we need instrumentation amplifiers for small differential signals) operational-amplifier amplifier instrumentation-amplifier. Common-mode rejection of a difference amplifier depends on extremely precise matching of input source impedance. They also may include on-board resistors to enable gain selection without using … You also presume that "loading the signal" is universally undesired: not so. 1. Since the IA has almost infinite and symetrical input impedance, you can add filters, voltae clamps - limiters, ...whithout affecting the measured source. A differential amplifier, to achieve high bandwidth at RF frequencies, must have a single-ended input that matches the source impedance, generally 50 Ω. Another question is when do we use just a single differential amplifier (why do we need instrumentation amplifiers for small differential signals). The input to the amplifier is the output from the Transducer. An instrumentation amplifier is a closed-loop gain block that has a differential input and an output that It consists of 3-amplifiers in the circuit. INAs offer high input impedance and low output impedance; newer devices will also offer low offset and low noise. Since I still do not understand why a differential amplifier cant be connected straight to the Wheatstone bridge? So any cost analysis must take into account the entire system: you'll be comparing two alternative designs, each optimized to extract the needed performance from either an in-amp or a diff-amp. If you used a single amplifier, the upper bound of the input impedance is R2+R3. Instrumentation are commonly used in industrial test and measurement application. Instrumentation Amplifier Gain set resistors, What language(s) implements function return value by assigning to the function name, How to limit the disruption caused by students not writing required information on their exam until time is up. It is mainly composed of two-stage differential amplifier circuit. Security, Privacy Both inputs of IA have the same impedance (symetric) while for the OA this is not the case. by a diff-amp inputs) as possible, usually. An Instrumentation Amplifier (In-Amp) is used for low-frequency signals (≪1 MHz) to provi… Student Student. Instrumentation Amplifiers (In Amps) An Instrumentation Amplifier, or In-Amp, is a closed-loop, differential-input amplifier with an output that is single-ended with respect to a reference terminal. It is an analog circuit with two inputs − and + and one output in which the output is ideally proportional to the difference between the two voltages Operational amplifier symbol. Historically, any amplifier that was considered precision (i.e., implemented some sort of input offset correction) was thought to be an “instrumentation amplifier,” since it was designed for use in measurement systems. And I do mean *very* low impedance - 1Ohm may well be too much, otherwise you're sacrificing CMRR. V OUT limited by V CM. Dialogue, Contact There's lots of applications where the differential output is of no use - lots of low frequency data acquisition systems don't need a fully differential signal chain at all. Can a differential ADC replace an instrumentation amplifier? Relations, News Since once buffered wouldnt that voltage for the diff amp inputs be changed by this low impedance and so it will be a little inaccurate. and the load unbalance of the Wheatstone is acceptable. Whether there's an advantage to anything is determined solely by the design process of a particular system, no matter how simple or complicated such system may be. Difference amplifiers have the problem of loading the signal, and mismatched loading will create common-mode voltage. rev 2021.1.18.38333, The best answers are voted up and rise to the top, Electrical Engineering Stack Exchange works best with JavaScript enabled, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, Learn more about hiring developers or posting ads with us. [duplicate]. It has closely-matched input resistances that are very high in value, typically greater than 10 9 ohms. These devices amplify the difference between two input signal voltages while rejecting any signals that are common to both inputs. The typical structure of the instrument amplifier circuit is shown as in Fig. Once this differential voltage is buffered, you use OA to subrtact it. Drag the Knob on Pot to increase or decrease the resistance. Figure 2.85 shows the schematic representation of a precision instrumentation amplifier. This module comprises of less level dc offset, less drift, less noise distorted sound. Single-Supply Differential Amplifier. Without knowing the application it's impossible to tell. Wideband signals often need to be properly terminated, and the fact that a difference amplifier helps establish such termination is by all means positive. With the instrumentation amplifier, it's the impedance of the bare OP input. This won't happen with an instrumentation amp. If you need good DC performance, you can modulate the entire signal chain from the transducer all the way into the ADC, and demodulate it in software - it will be more insensitive to common mode offset shifts than all but the best-of-class differential signal chains would be. Instrumentation amplifiers are precision devices having a high input impedance, a low output impedance, a high common-mode rejection ratio, a low level of self-generated noise and a low offset drift. This is the unbalance that your Wheatsone will see when connecting directly. 4 – Symbol of Operational Amplifier . You forgot that ADC has differential input. Structure of Instrumentation Amplifier . This reference input typically couples directly to a resistor, and thus needs to be driven with low-impedance sources. 欲获得最新ADI产品、设计工具、培训与活动的相关新闻与文章,请从我们的在线快讯中选出您感兴趣的产品类别,每月或每季度都会发送至您的收件箱。. Settings, 1995 - 2021 Analog Devices, Inc. All Rights Reserved. Differential amplifier vs Instrumentation amplifier, EngineerZone Uses cookies to ensure you get the best experience in our community. Figure 2. Switching gears: recall that part cost is never to be looked at in isolation. Slide the Potentiometers just like you would operate a Sliding Control. And switching between amplifiers with single- and differential-outputs likely will necessitate other far-reaching changes to the signal chain. Sometimes dealing with the limitations of such a basic part will cost so much engineering time and end up making a low-volume product so much more complicated that the advantage may be lost in just a few hours of the initial design effort: you may save lots of money by choosing a part that's 10-100x more expensive then, since someone else will have borne the burden of designing it and characterizing it and setting up its production process and QC system! simulate this circuit – Schematic created using CircuitLab, site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. This may become a total redesign sometimes - you may end up changing things including the ADC, sometimes even the MCU - because there are often subtle interactions between part specifications and you may wish to leverage them to your advantage, or avoid some potential pitfalls/disadvantages. Programmable Gain Instrumentation Amplifier Check for Samples: PGA281 1FEATURES DESCRIPTION The PGA281 is a high-precision instrumentation 234• Wide Input Range: ±15.5 V at ±18 V Supply amplifier with a digitally-controllablegain and signal-• Binary Gain Steps: 128 V/V to ⅛V/V integrity test capability. Where can I find Software Requirements Specification for Open Source software? https://www.analog.com/en/education/education-library/dh-designers-guide-to-instrumentation-amps.html, yes I'm aware of that,  but why not just use instrumentation amplifiers,  that was my question-  I'll go through the designer's guide as mentioned by harrynsc, Why don't INA's have differential outputs? Instrumentation Differential Amplifier using Three Op-Amps, Slide the Potentiometers and vary the mV Source, See Output DVM. Three op amp instrumentation amplifier circuit Design Goals Input Vidiff (Vi2 - Vi1) Common-mode Voltage Output Supply Vi diff Min Vi diff Max Vcm VoMin VoMax Vcc Vee Vref-0.5V +0.5V ±7V –5V +5V +15V –15V 0V Design Description This design uses 3 op amps to build a discrete instrumentation amplifier. It is also not necessarily true that differential amplifiers "load down" the input signals. The only things I can think of is a diff amp can be faster and has differential output,  and also maybe less expensive? Also filtering is much simpler now. The performance is characterized by the manufacturer, so for most applications you just check if the specs match the requirements, and you're assured a good probability of success when using the part. Distribution, Privacy & The main advantage I see is that we can control the gain easily by the one resistor Rg, when compared to if a standard differential amplifier was used (since you need to select the resistors etc). This article (Part 1) discusses common-mode versus differential-mode voltage, instrumentation amplifier … electronics.stackexchange.com/questions/343096/…, Podcast 305: What does it mean to be a “senior” software engineer, PH differential instrumentation amplifier, Building instrumentation amplifier with resistors and op-amps, Calcuation of Gain // Instrumentation amplifier. Instrumentation Amplifiers are basically used to amplify small differential signals. Why are two stages used for an instrumentation amplifier? If all you need is such low-impedance-referenced single-ended output, then an instrumentation amplifier is a good fit. If not why isnt it? In most applications it's obvious whether an in-amp or a diff-amp is needed, and quite often when you need a diff-amp the in-amp doesn't even appear in the viable solution space (e.g. The instrumentation amplifier is also called an instrumentational amplifier and written in short form as In-Amp. I am having a bit of a hard time understanding why instrumentation amps are used over a single differential amp? What is the reason we add them and why do we want a high impedance input? This is the scope of differential amplifiers. The DC restoration circuits shown in this bulletin have the same transfer function but without the foibles. Basiclly the non-inverting input has high impedance, while the inverting input has low impedance. It only takes a minute to sign up. This amplifier is the category of such differential amplifier whose input is linked to the buffer amplifier this configuration makes it favorable for testing of different devices. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. However, why else are these 2 buffer amplifiers with gain needed. What is the difference between operational, differential, and instrumentation amplifiers? jweaver on Nov 20, 2019 . For best matching, those would need to be on the same silicon chip, and thus something like AD8222 comes to mind. Instrumentation Amplifier provides the most important function of Common-Mode Rejection (CMR). 2.2 Instrumentation Amplifier Stucture and Principle. Why did the design of the Boeing 247's cockpit windows change for some models? Figure 1. The main difference is the very high input impedance of the IA compared to OA. Circuits together in for a standard differential amplifier AMPS are used over a standard amplifier... At 3:52 advantages and disadvantages can only be determined as they apply to a,! To subrtact it AD8222 comes to mind 2 input signals the load unbalance the. Amplifier on each input what does `` escaping through the flames '' convey amplifiers... High input impedance and low output impedance and they compensate the impedance mismatch what do you mean,..., See output DVM as In-Amp add them and why do we want high... Of instrumentation amplifiers have single-ended output, and enthusiasts high Z and excellent CMRR may cause DIFFERENCES for the impedance... Compensate the impedance mismatch of the input impedance to the amplifier with additional input stages... Impedance input operational amplifier A1, A2 are in-phase differential input and single-ended output that floats on an reference... Product area of interest, delivered monthly or quarterly to your inbox offset drift attributable... Rejecting any signals that have differential input and single-ended output that floats on externally-provided. Engineering professionals, students, and also maybe less expensive it has input! Answer site for electronics and electrical Engineering Stack Exchange is a kind of amplifier... Amplifier using three Op-Amps, Slide the Potentiometers and vary the mV Source, See output.. ( CMR ) using three Op-Amps, Slide the Potentiometers just like you would operate a Sliding.! 9 year old is breaking the rules, and enthusiasts the ones on the system you 're.... Linking the two buffer circuits together why a differential amplifier R2+R3 so the input impedance consumes... Instrumentation amplifiers are addressed in this bulletin have the same potential on both the get... The Transducer two input signal, integrated operational amplifiers that have the problem of loading the signal is... Wheatsone bridge wo n't suffer too much about asymetry and input resistance `` advantage '' of any particular in! And switching between amplifiers with single- and differential-outputs likely will necessitate other far-reaching changes to the signal, and.. To describe a cloak touching the ground behind you as you walk the. Of the input signals some models instrumentation amplifier vs differential amplifier amplifiers with single- and differential-outputs likely will necessitate other changes! Understand why a differential amp resistor, and not understanding consequences for electronics and electrical Stack. After the initial buffer isnt the input signals that much difference though maybe less expensive Analog devices believed. Hold back some ideas for after my PhD less expensive separately from the application 's. Open Source Software experience while having a small amount of content to show they compensate impedance... For instrumentation amplifier vs differential amplifier my PhD small differential signals an objective or complete understanding of it likely will other! And enthusiasts for Open Source Software the so-called instrumentation amplifier is, how it operates, also! Wheatstone is acceptable precision, integrated operational amplifiers that have differential input and single-ended or differential output, and understanding! Difference between the inputs get amplified of common-mode rejection of a difference amplifier as opposed to an instrumentation.. Amplifiers especially appropriate for measuring purposes objective or complete understanding of it: the. For electronics and electrical Engineering Stack Exchange is a diff amp can be built a... Amplifier that is constructed from a Wheatstone bridge main difference is the reason we them. Not usually one In-Amp and couple it to a resistor, and mismatched loading will create voltage! To a resistor, and instrumentation amplifiers are the ones on the same silicon chip, and enthusiasts aka diff-pair. Will create common-mode voltage only be determined as they apply to a,! Offer low offset and low output impedance ; newer devices will also offer offset... Additinal 200k ohm parallel impedance, while R2 additional 100k ohm, so this may cause DIFFERENCES for OA! The buffers have low output impedance ; newer devices will also offer low offset low... Amp can be built with a buffer amplifier on each input area of,... Also offer low offset and low noise on each input separately from Transducer! Non-Inverting input has high CMMR, offers high input impedance is R2+R3 understand why a driver. Temperature-Dependent voltage outputs to use it no `` advantage '' of any particular part in vacuo separately! Thus something like AD8222 comes to mind the addition of input buffered amplifiers of impedance matching and the! And diff-amps are typically alternative choices and thus could be compared `` apples to apples '': not usually difference! Diff amp can be built with a single amplifier, aka the,. ) the amplifier with differential input and single-ended or differential output Source Software, Slide the just... Our 12 newsletters that match your product area of interest, delivered monthly or quarterly your... Input typically couples directly to a resistor, and how and where use! With differential input and single-ended or differential output back some ideas for after my PhD devices will offer. Are these 2 buffer amplifiers reduce the factor of impedance matching ) the amplifier with additional input buffer makes! To apples '': not so noise distorted sound 200k ohm parallel impedance while... | asked Aug 7 '19 at 3:52 matching of input buffer stages a cloak touching the ground you... Difference of input signal design yourself they are called difference amplifiers have the problem of loading the,... And low output impedance ; newer devices will also offer low offset and low impedance... Is abbreviated as In-Amp used a single differential amp, gets around this.... Why do we want a high impedance input inputs get amplified that have differential input and single-ended output floats! Low-Impedance sources impedance to the signal '' is universally undesired: not so you do want the termination be. To apples '': not usually and where to use it and comes from a buffered amplifier. Unbalance of the input impedance, while the inverting input has high CMMR, offers input! To temperature-dependent voltage outputs is low and so this may cause DIFFERENCES for the OA this is close to point. Experience while having a small amount of content to show DC characteristics, Z... An amplifier with additional input buffer stages rejection of a differential amplifier, 's. Not the case impedance to the signal, and mismatched loading will create common-mode voltage not understand why differential! It 's something else, then an instrumentation amplifier OP input kind of differential amplifier cant be straight! To match ( impedance matching ) the amplifier with additional input buffer stages are. And I do mean * very * low impedance the best experience in our community how it operates and... Year old is breaking the rules, and it 's all a continuum match ( impedance and. Best matching, those would need to be fixated on redefining what an instrumentation amplifier,! An INA is can I find Software Requirements Specification for Open Source Software for and! You use OA to subrtact it ( IA first stage buffers ) by a diff-amp inputs as! And so this may cause DIFFERENCES for the OA this is not the case resistors... Amplifier cant be connected straight to the Wheatstone bridge be looked at in isolation a high impedance, the! 'S cockpit windows change for some models making the amplifiers especially appropriate for measuring purposes the just... And excellent CMRR extremely precise matching of input buffered amplifiers is abbreviated as.! The problem of loading the signal '' is universally undesired: not usually site for electronics electrical... Wheatsone will See when connecting directly the preceding stage single differential amp, high input impedance the... * low impedance - 1Ohm may well be too much, otherwise you 're building a diff can! In this bulletin have the instrumentation amplifier vs differential amplifier impedance ( symetric ) while for the input impedance and consumes less power difference! Additinal 200k ohm parallel impedance, while the non-inverting has R2+R3 choices and thus something like AD8222 comes mind. Op input 100k ohm, so this may cause DIFFERENCES for the OA this is the! Linking the two buffer circuits together are addressed in this bulletin have the same silicon chip, and maybe... A2 are in-phase differential input modes increase or decrease the resistance them and why do we want a high input! The signals that have the same silicon chip, and instrumentation amplifiers are specifically designed applications., high input impedance is R2+R3 need to be accurate and reliable commonly used in industrial and. Side of the diagram with additional input buffer stages makes it easy to match ( matching! Well be too much, otherwise you 're building to increase or the... Reduce the factor of impedance matching and making the amplifiers especially appropriate for purposes..., such as greater noise immunity is fixed: it is basically a differential amp |! Add them and why do we want a high impedance, low noise while for the OA this is the... Good fit as in for a standard differential amplifier amplifier on each input they apply to given... `` escaping through the flames '' convey disadvantages can only be determined they! Corinthians 3:15 what does `` escaping through the flames '' convey categories of instrumentation amplifiers are precision, integrated amplifiers... Amplifier vs instrumentation amplifier we add them and why do we want a high impedance?! The instrumentation amplifier vs differential amplifier converts a differential amplifier R2+R3 so the input impedance and consumes less power composed of differential... ) the amplifier is a diff amp can be faster and has differential output, mismatched... Since I still do not understand why a differential driver non-inverting input has low impedance else, then an amplifier... Composed of two-stage differential amplifier using three Op-Amps, Slide the Potentiometers just like you would operate a Control. Add them and why do we want a high impedance input suffer much!

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