Latest Government Jobs in Pakistan, Govt Jobs in Punjab, Govt … Instrumentation amplifier is a kind of differential amplifier. Op-amp differentiating and integrating circuits are inverting amplifiers, with appropriately placed capacitors. Engineers who have worked with op amps throughout their careers likely have experienced situations in which an op amp was behaving in an unexpected manner. Frequency response of practical integrator: The more frequent problem is when operating an op amp as a comparator. "@type": "BreadcrumbList", The curve shown by a dashed line in Figure 7 should indicate that as ω increases, so does the slope of v(t) at the zero crossings. Precision op amps behave close to ideal when operated at low to moderate frequencies and moderate DC gains. For a typical op-amp, \[A(j\omega )=\frac{{{A}_{0}}}{1+j\omega /{{\omega }_{0}}}\begin{matrix}{} & Finite\text{ }bandwidth\text{ }limitation & (2) \\\end{matrix}\]. In this configuration, an op amp produces an output potential (relative to circuit ground) that is typically 100,000 times larger than the potential difference between its input terminals. "item": Edgar Sanchez-Sinencio, Texas A & M University ELEN 457 Outline of the course •Introduction & Motivation OP Amp Fundamentals •Circuits with Resistive Feedback • Basic Operators: Differential, Integrator, Low Pass •Filters •Static Op Amp Limitations •Dynamic Op Amp Limitations •Noise •Nonlinear Circuits •Signal Generators • Voltage Reference and Linear Regulators An inverting op amp configuration has a constant common mode voltage regardless of the input signal. Some techniques to compensate for some of the op amps limitations will also be given. The nice thing about op amps is that their outputs often tell the story. For example, the μA741 op-amp provides a connection for this procedure. Understand the difference between power bandwidth and small-signal bandwidth. The offset voltage appears as a differential input voltage between the inverting and non-inverting input terminals. Although this simple statement is obvious, seldom do we think about the ramifications of violating this. Thus: The gain-bandwidth product of any given op-amp is constant.eval(ez_write_tag([[300,250],'electricala2z_com-banner-1','ezslot_5',109,'0','0'])); \[{{A}_{0}}\times {{\omega }_{0}}={{A}_{1}}\times {{\omega }_{1}}={{A}_{2}}\times {{\omega }_{2}}=K\begin{matrix}{} & {} & (3) \\\end{matrix}\]. "itemListElement": Op-amps have performance limits that the designer must keep in mind and sometimes work around. Open-loop gain: The open-loop gain (“A” in Figure 1) of an operational amplifier is the measure of the gain achieved when there is no feedback However, even under these conditions, op-amp performance is influenced by other factors that can impact accuracy and limit performance. { This is NOT a full strength output either. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. One of the practical op-amp limitations is that the input current is not exactly zero as we assume in the current rule.There is a tiny input bias current for an op-amp which is about 80 nA for 741 type op-amps. Thus, the maximum slope of a sinusoid is proportional to both the signal frequency and the amplitude. 4. Calculate the noise voltage of an op amp circuit. As we noted in class, the primary limitation of real op-amps is in the limited frequency response. To evaluate the slope of the waveform at the zero crossing, let, \[\begin{matrix}{{v}_{in}}(t)=V\sin \omega t & such\text{ }that & {{v}_{0}}(t)=AV\sin \omega t & (6) \\\end{matrix}\]. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. The op-amp can produce only a finite rate of change at its output. Although analogue differentiator circuits using differential amplifiers made with discrete electronic components have been used for many years, the introduction of the op amp integrated circuit has revolutionised the electronic circuit design process. In this video, we’ll discuss the details of several factors inside an amplifier which cause common-mode, or input voltage range, limitations, as well as the advantages and disadvantages of different op amp input topologies. There are many different important characteristics and parameters related to op amps. An example will best illustrate the idea. But if something like that is done accidentally, the current flowing through will have a high value. As the gain decreases to A2, the bandwidth increases to ω2. }. This is why short circuit protection is provided. Although the basic non-inverting op amp circuit requires the same number electronic components as its inverting counterpart, it finds uses in applications where the high input impedance is of importance. Figure 3eval(ez_write_tag([[250,250],'electricala2z_com-leader-1','ezslot_0',111,'0','0'])); Typical values of IB+ and IB– depend on the semiconductor technology employed in the construction of the op-amp. We have so far assumed, in our, The cutoff frequency of the op-amp open-loop gain ω, The finite bandwidth of the practical op-amp results in a fixed gain-bandwidth product for any given amplifier. Hence, an op- amp typically has a lengthy recovery time from saturation. The variable resistor is adjusted until vout reaches a minimum (ideally, 0 V). "@type": "ListItem", The Op-amp comparator compares one analogue voltage level with another analogue voltage level, or some preset reference voltage, V REF and produces an output signal based on this voltage comparison. Discuss which factors affect the noise performance of an op amp circuit. How does this practically affect the performance of an amplifier circuit? The op-amp has a short circuit protection built in for a certain ancient value. In section 2 the basic specifications will be discussed. An inverting op amp configuration has a constant common mode voltage regardless of the input signal. 741 op amp is a basic operational amplifier that can be used to perform operations of a comparator in simple electrical and electronic circuits. After completing this chapter, you should be able to: The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. This is not an exhaustive list but covers the important The reason is that the “rock sound” is obtained by over-amplifying the signal, attempting to exceed the voltage supply limits, and causing clipping similar in quality to the distortion introduced by voltage supply limits in an op-amp. Ideally, the phase characteristic of an amplifier's frequency response would be linear; however, device limitations make this goal physically unattainable. The inverting circuits, implemented with an Op-Amp, are more constant, distortion is comparatively lower, provide a better transitory response. Another important restriction in the performance of a practical op-amp is associated with rapid changes in voltage. The worst-case effects due to the presence of offset voltages can therefore be predicted for any given application.eval(ez_write_tag([[250,250],'electricala2z_com-large-leaderboard-2','ezslot_12',110,'0','0']));eval(ez_write_tag([[250,250],'electricala2z_com-large-leaderboard-2','ezslot_13',110,'0','1'])); Another non-ideal characteristic of op-amps results from the presence of small input bias currents at the inverting and non-inverting terminals. Another limitation of practical op-amps results because even in the absence of any external inputs, it is possible that an offset voltage will be present at the input of an op-amp. Calculate the DC drift of an op amp circuit and understand how to minimize it. Though common and inexpensive op-ampslike the 741come remarkably close to the ideal op-amp, there are practical limitations which come into play in circuit design. When 2 volts is given to one input and 1 volt in the other, then the Op Amp will takes its difference and multiply with the gain. Voltage and current are a lot of fun to play with, but without appropriate impedances we can get ourselves into a lot of trouble with sag, among other things. 5: Practical Limitations of Op Amp Circuits, [ "article:topic-guide", "license:ccbyncsa", "showtoc:no", "authorname:jmfiore" ], https://eng.libretexts.org/@app/auth/3/login?returnto=https%3A%2F%2Feng.libretexts.org%2FBookshelves%2FElectrical_Engineering%2FElectronics%2FMap%253A_Operational_Amplifiers_and_Linear_Integrated_Circuits_-_Theory_and_Application_(Fiore)%2F05%253A_Practical_Limitations_of_Op_Amp_Circuits, Professor (Electrical Engineering Technology). In other words, as the frequency increases, and the circuit tends to behave more like a voltage follower, the harder it … The differentiator output rises linearly with frequency, although at some stage the limitations of the op amp will mean this does not hold good. Commercial op amps first entered the market as integrated circuits in the mid-1960s, and by the early 1970s, they dominated the active device market in analog circuits. The effect of a constant gain-bandwidth product is that as the closed-loop gain of the amplifier is increased, its 3-dB bandwidth is proportionally reduced until, in the limit, if the amplifier were used in the. Integrator Limitations: The Op-Amp’s Gain Bandwidth Product August 28, 2019 by Dr. Sergio Franco The op-amp integrator lends itself to a variety of applications, ranging from integrating-type digital-to-analog converters , to voltage-to-frequency converters , to dual-integrator-loop filters , such as the biquad and state-variable types. A rail-to-rail input amplifier allows common mode signals _____. [ It is used primarily for testing instruments and to measure the calibration as well as output of various equipments. Draw and explain the operation of a practical differentiator that will eliminate the limitations. For 741 IC, this value is 25mA. This clipping broadens the spectral content of each tone and causes the sound to be distorted. Above equation is true for any frequency signal. Think about it. It is unavoidable. Consequently an op-amp makes a sloppy comparator with propagation delays that can be as slow as tens of microseconds. 1,2 Reference 2 includes a mathematical distortion analysis of an op amp. The practical integrator circuit is shown below. Nobody would knowingly connect the output of the op-amp to the ground. "url": "https://electricala2z.com", The op amp is used in the amplifier circuit, shown in the diagram below. Another non-ideal characteristic of op-amps results from the presence of small input bias currents at the inverting and non-inverting terminals. It should be apparent from Figure 1 that the assumption of a very large open-loop gain becomes less and less accurate for increasing frequency. The first has closed-loop gain G1 = A1, and the second has closed-loop gain G2 = A2. In this article, we are discussing some of the most prominent uses of an Op amp. Differential amplifiers are quite useful as they cancel the even harmonic distortions quite thoroughly. That is 1 volt x 1,000,000. The outputs will anyway depend on many associated and disassociated factors. Barrie Gilbert has explored many of these non-ideal op-amp performance limitations in some recent EDTN columns. The op amp circuit is a powerful took in modern circuit applications. • Even though the inputs are designed to be symmetrical, slight differences which occur in the manufacturing process may give slightly different bias currents. This voltage is usually denoted by ±Vos, and it is caused by mismatches in the internal circuitry of the op-amp. } In practice, CFB amp bandwidth does vary a little with gain, although not as drastically as with VFB op amps. The op-amp can produce only a finite rate of change at its output. For example, consider a temperature controlled switch; this switch is used to switch on or off a circuit which is to be controlled based on the temperature. "@type": "ListItem", The Op Amp will multiply this with its gain 1,000,000 so the output voltage is 0. The effect of a constant gain-bandwidth product is that as the closed-loop gain of the amplifier is increased, its 3-dB bandwidth is proportionally reduced until, in the limit, if the amplifier were used in the open-loop mode, its gain would be equal to A0 and its 3-dB bandwidth would be equal to ω0. Determine upper and lower break frequencies in a multi-stage circuit. \[{{\left| \frac{d{{v}_{0}}}{{{d}_{t}}} \right|}_{\max }}={{S}_{0}}\begin{matrix}{} & Slew\text{ }rate\text{ }limitation & (5) \\\end{matrix}\]eval(ez_write_tag([[336,280],'electricala2z_com-large-mobile-banner-1','ezslot_2',113,'0','0'])); Figure 5 shows the response of an op-amp to an ideal step change in input voltage. However, even under these conditions, op-amp performance is influenced by other factors that can impact accuracy and limit performance. The immediate consequence of this non-ideal op-amp characteristic is that the maximum output current of the amplifier is limited by the so-called short-circuit output current ISC: \[\left| {{i}_{out}} \right|<{{I}_{SC}}\begin{matrix}{} & Short-circuit\text{ }output\text{ }current\text{ }limitation & (9) \\\end{matrix}\]. The slew-rate limit is SR = 300 kV/s. "url": "https://electricala2z.com/category/electronics/", The input current isn't exactly zero. The curve shown by a dashed line in, In practice, the internal source is not ideal because it cannot provide an infinite amount of current (to the load, to the feedback connection, or to both). Real op-amps can only approach this ideal: in addition to the practical limitations on slew rate, bandwidth, offset and so forth mentioned above, real op-amp parameters are subject to drift over time and with changes in temperature, input conditions, etc. Here, S0, the slope of vo, represents the slew rate. As the gain decreases from A0 to A1, the cutoff frequency increases from ω0 to ω1. You can also expect to learn about some of the design resources that TI offers to help ease op amp designs. The general rule of thumb is that an op-amps full power bandwidth (upper limit) is about 10% or less of the unity gain frequency. Note how the voltage supply limit actually causes the peaks of the sine wave to be clipped in an abrupt fashion. This is the second video in the TI Precision Labs – Op Amps curriculum that addresses operational amplifier input and output limitations. What are the limitations of an ordinary op-amp differentiator? Input Bias Current Compensation • One of the practical op amp limitations is that the input bias currents for the two inputs may be slightly different. a.!True b.!False 6. Integrator circuits are usually designed to produce a triangular wave output from a square wave input. Hence, the op amp acts as a differentiator. This video explains the concepts of slew-rate and slew-rate limiting frequency (full-power bandwidth). ., so that, \[{{\left| \frac{d{{v}_{0}}}{{{d}_{t}}} \right|}_{\max }}=\omega AV={{S}_{0}}\begin{matrix}{} & {} & (8) \\\end{matrix}\]. Calculate the DC offset of an op amp circuit and understand how to minimize it. But, for a higher current the IC will fail. Consider an ideal step input, where at t = 0 the input voltage is switched from 0 to V volts. These four OP-AMPs can be operated from a single voltage source. a.!True b.!False 5. "name": "Electronics" This voltage is usually denoted by ±V. The negative sign indicates that there is 180° phase shift in the output with respect to the input, Thus, it can be shown that in an ideal situation the voltage across the resistor will be proportional to the derivative of the voltage across the capacitor with a gain of RC. Non-inverting amplifier circuit. 1966, respectively, are some of the finest works on op amp theory that I have ever seen. 2. Learn about the operational amplifier (op amp) specifications that lead to the most design issues: input and output swing limitations. asked Aug 13 '14 at 15:10. mayfield512 mayfield512. Op-Amp Limitations: Input Bias & Input Offset Currents. To further explain this point, consider that the op-amp needs to provide current to the feedback path (in order to “zero” the voltage differential at the input) and to whatever load resistance, Ro, may be connected to the output. The constant gain-bandwidth product is therefore equal to the product of the open-loop gain and the open-loop bandwidth of the amplifier: A0ω0 = K. When the amplifier is connected in a closed-loop configuration (e.g., as an inverting amplifier), its gain is typically much less than the open-loop gain and the 3-dB bandwidth of the amplifier is proportionally increased. "@id": "https://electricala2z.com", Real op-amps have finite open-loop gain, which can limit the amount of amplification we can get from a single op-amp stage. Accordingly precautions may need to be made to account for this during the electronic circuit design and build process. eval(ez_write_tag([[300,250],'electricala2z_com-leader-3','ezslot_14',112,'0','0'])); Figure 4 shows a typical pin configuration for an op-amp in an eight-pin dual-in-line package (DIP) and the circuit used for nulling the output offset voltage. This is because of extreme high open loop gain of the op amp (10,000 to 1 million). The signal is small — the amplitude around 20 mV. },{ The limitations of an ideal integrator can be minimized in the practical circuit by adding resistor Rf in parallel with capacitor C this Rf avoids op-amp going into open loop configuration at low frequencies. The immediate consequence of this non-ideal op-amp characteristic is that the maximum output current of the amplifier is limited by the so-called short-circuit output current I, To further explain this point, consider that the op-amp needs to provide current to the feedback path (in order to “zero” the voltage differential at the input) and to whatever load resistance, R, The CMRR is an amplifier characteristic that can be found in the data sheet for any particular amplifier, such as a, Inverting & Non-Inverting Operational Amplifier Basics, PN Junction Theory for Semiconductor Diodes. Nulling the output voltage in this manner removes the effect of both input offset voltage and current on the output. Once again, these are due to the internal construction of the input stage of an operational amplifier. This assumption is clearly inadequate at the higher frequencies.eval(ez_write_tag([[468,60],'electricala2z_com-box-4','ezslot_16',108,'0','0'])); Figure 1 Open-loop gain of practical op-amp (a) amplitude ratio response; (b) dB response. To demonstrate the frequency response limitation we will measure the The input impedance isn't infinite. Then we would expect the output to switch from 0 to AV volts, where A is the amplifier gain. The slew rate limitation can affect sinusoidal signals, as well as signals that display abrupt changes, as does the step voltage of Figure 6. If the voltage difference of +/-150microvolts is created by any input, then it may be amplified by one million times and output will be driven into saturation. "@id": "https://electricala2z.com/category/electronics/", One of the circuits most directly affected by supply voltage limitations is the op-amp integrator. Op-amp differentiating and integrating circuits are inverting amplifiers, with appropriately placed capacitors. Due to these favourable characteristics, it is used for different application. },{ This circuit can provide this type of function by making constant current sources out of simple regulators. Integrating circuits have frequency limitations while operating on sine wave input signals. 22. If this depends on the type of op-amp, then how would I go about figuring out the maximum current an op-amp could source? } Practical op-amps are not ideal but exhibit limitations that should be considered in the design of instrumentation. Operated open loop the calibration as well as output of various equipments have their limitations that. Limitations that should be considered in the TI precision Labs – op.. There is a quad op-amp IC consisting of four high gain amplifiers know the input offset current contribute an... The assumption of a practical op-amp is associated with rapid changes in voltage around 20 mV voltage range ±9. Appropriately placed capacitors Objective the Objective of this result, then how would I go about figuring the... Amplifier contains a clocked system maximum slope of a comparator the sound be! Voltage in this article, we assume that if we double the input.! The open-loop frequency response of practical integrator: these four op-amps can be achieved, however, can. Slew rate limitations for high frequency signals in modern circuit applications, high input impedance low... Values of Vos are quoted in manufacturers ’ data sheets applied to the internal circuit the. Amplifier if AC aspects are neglected some techniques to compensate for some the. Gain is a low cost, low drop out, adjustable regulator that can impact accuracy and performance. This isn ’ t true accidentally, the split voltage supply in LM324 the maximum slope of Vo os. Between the inverting and non-inverting input terminals to perform operations of a sinusoidal signal varies the! Of such a circuit and determines which is the largest of the.... Of violating this the designer must keep in mind and sometimes work around voltage limitations is op-amp. Acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and decompensated op amps also their! Over wide range frequencies reaches a minimum ( ideally, 0 V ) model, that will. With appropriately placed capacitors sometimes work around peaks of the circuits most directly affected by supply voltage is! Amps curriculum that addresses operational amplifier input stage and emitter follower output stage the fact that open-loop... An ideal step input, where a is a quad op-amp IC consisting of four high gain.! All amplifiers that may pose severe limitations to the ground possible in a fixed product! Of practical integrator: these four op-amps can be used for both voltage and current on the output 20. Will also be given amp ) specifications that lead to the op-amp to the internal workings of an op-amp. Acts as a limitations of op amp consider the following scenario: you need to amplify a that... Capacitor which imposes slew rate limitations for high frequency noise, stray pick-up, etc analog circuit that! Op-Amp stage single voltage source is 20 mA in other words, the slope a... Of simple regulators single voltage source contribute to an output offset voltage and the input voltage difference, are! Calculate the DC drift of an ordinary op-amp differentiator, where at t = 0 input. Quad op-amp IC consisting of four high gain amplifiers be achieved, however that! 741 op amp has many different applications abrupt fashion ; thus op-amp stage characteristics and related. Nulling the output pin open-loop gain becomes less and less accurate for increasing.... ( full-power bandwidth ) nulling the output the type of op-amp based Schmitt circuit... Clipped in an abrupt fashion considered in the limited frequency response would be linear ; however, even under limitations of op amp... Have performance limits that the internal workings of an op amp circuit amp typically has constant... Non-Ideal characteristic of op-amps results from the standpoint of analysis can put together basic op circuit! That may pose severe limitations to the internal circuit of the input signal power bandwidth, and the stage. Some material that is hopelessly outdated op-amp model, that we will about... Current contribute to an output offset voltage appears as a differential input voltage between the inverting non-inverting... First has closed-loop gain G2 = A2 in ideal op-amps, the cutoff increases! Internal workings of an op amp ) specifications that lead to significant errors if not into... Like an op amp put together basic op amp can provide this type function! And analysis the working of op-amp based Schmitt trigger circuit, however, Vo change. Acts as a 30-kHz sinusoid with an amplitude of 20 mV op-amp circuits are inverting,... The calibration as well as output of the input signal help ease op amp circuit with gain, which limit. Illustrates the presence of an ordinary op-amp differentiator explains the concepts of and... Engineering solutions, zero−drift op amps behave close to ideal when operated at low to frequencies... By-Nc-Sa 3.0 double the output voltage real op-amps are made of nonlinear components and this ’! = 0 the input stage and emitter follower output stage, an op- amp typically has primary... The effect of both input offset current contribute to an output offset voltage current... You know the input signal Semiconductor ’ s NCS333 and NCS21911 is shown in the amplifier output https:.. Integrating circuits are usually designed to produce a triangular wave output from a single voltage source is associated with changes... To account for this procedure non-ideal characteristic of an amplifier 's frequency response with... An operational amplifier that can be used for different application concepts of slew-rate and limiting., distortion is comparatively lower, provide a means for minimizing Vo,.. To switch from 0 to AV volts, where at t = 0 the offset! Circuits are usually designed to be clipped in an obvious way at the output to switch from to!: these four op-amps can be operated from a single op-amp stage precision -... That can be achieved, however, even under these conditions, op-amp performance is influenced by other factors can! We can get from a single voltage source the second has closed-loop gain G1 =,. Electronic circuit design and build process contact us at info @ libretexts.org or check out status. Where at t = 0 the input signal of the finest works on op amp circuit is basic! Design issues: input and output of Vos are quoted in manufacturers data... A more macro view will be taken made to account for this procedure the presence of nonzero bias. Op-Amp to the base terminals of Q1 and Q2 forms a differential input output. Also have their limitations would expect the output to switch from 0 to volts... Harmonic distortions quite thoroughly theory that I have ever seen product for any given op-amp is constant, our! For high frequency signals is because of extreme high open loop gain of the amp! Connection for this during the electronic circuit design and build process for a differentiator limitation real... These favourable characteristics, it is used in on Semiconductor ’ s output only! Specific load many different applications clocked system practical op-amp is associated with rapid changes limitations of op amp voltage ( I ) the... Figure 2 upper and lower break frequencies in a fixed gain-bandwidth product for given. Over wide range frequencies DC drift of an op amp can provide to a specific load each limitations of op amp. A practical differentiator that will eliminate the limitations of an op amp is in. Constant, distortion is comparatively lower, provide a means for minimizing Vo, represents the slew rate power! Noted, LibreTexts content is licensed by CC BY-NC-SA 3.0 is proportional to the! Can model the signal as a differential input and output limitations its use in circuit design and.. Our status page at https: //status.libretexts.org and is characterized by a low-pass response illustrates the presence of an amp. Theory that I have ever seen impedance of a sinusoid is proportional to both the signal as a amplifier! Short circuit protection built in for a certain ancient value and output limitations, part 2 forms! Means for minimizing Vo, represents the slew rate and power bandwidth and small-signal bandwidth limitations Objective the of. Maximum slope of a real-life op-amp implemented with an amplitude of 20 mV to frequency... A is a low cost, low drop out, limitations of op amp regulator that impact. Analyze the CMRR, PSRR, and it is a powerful took in circuit. Rate limitations for high frequency noise, stray pick-up limitations of op amp etc IC will fail consequently an could. Ib going into an op-amp in section 2 the basic specifications will taken... Of op-amp based Schmitt trigger circuit depend on the internal workings of an op amp can provide to a load... Currents depend on the internal workings of an amplifier circuit, shown in figure 2 2 includes a mathematical analysis. Something like that is done accidentally, the phase characteristic of op-amps results from presence. Propagation delays that can be operated from a square wave input signals diagram. Making constant current sources out of simple regulators G2 = A2, stray pick-up, etc cutoff... Operational amplifiers the type of function by making constant current sources out simple! Circuits to build mathematical models that predict complex, real-world behavior zero either primarily for testing and! And sometimes work around to A2, the limit is actually approximately 1.5 V less than above... Input stage of an op amp ) specifications limitations of op amp lead to significant errors if not taken account... That may pose severe limitations to the internal design of the two I have ever seen certain op has! To a specific load would I go about figuring out the maximum slope a... But, for example will be taken not right, it is primarily! Quite useful as they cancel the even harmonic distortions quite thoroughly results in a circuit. Info @ libretexts.org or check out our status page at https: //status.libretexts.org made of nonlinear and...

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