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An antilog amplifier has a _____ in series with the input. d) 1.214(kT/q)v $V_{f}$ is the voltage drop across diode, when it is in forward bias. To practice all areas of Linear Integrated Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers. $I_{s}$ is the saturation current of the diode. An op-amp based logarithmic amplifier produces a voltage at the output, which is proportional to the logarithm of the voltage applied to the resistor connected to its inverting terminal. The electronic circuits which perform the mathematical operations such as logarithm and anti-logarithm (exponential) with an amplification are called as This set of Linear Integrated Circuit Multiple Choice Questions & Answers (MCQs) focuses on “Log and Antilog Amplifier”. b) log(x) c) VO = -(kT/q)×ln(Vref/Vi) Figure 2: Anti-logarithmic Amplifier IC with antilog element in input. Answer & Explanation Most Popular Articles. Though evolution of digital technology makes it easier to express real large numbers, but logarithm questions and solutions have not lost their relevance in the academic world. Complete Log/Antilog Amplifier External Components Not Required; Internal Reference; Temperature Compensated 6 Decades Current Operation-1 nA to 1 mA ... Offering both log and anti-log operation, model 755's price and performance are especial-ly attractive as … This section discusses about the op-amp based anti-logarithmic amplifier in detail. A. View Answer, 5. b) 0.597(kT/q)v Basically it performs mathematical operation of an anti-logarithm. The power is sometimes called the exponent. Log and Antilog Amplifier. It means zero volts is applied to its non-inverting input terminal. Here, y > 0, b > 0, and b ≠ 1. The compression of any wide-range input signal, analog computing circuits, linearization of exponential sources, such as transducers, certain types of audio circuits, compression and expansion circuits for voice communications. It is a non-linear amplifier used for amplification or compression of wide range of input signal for better resolution. a) In(x) Log amplifier or logarithmic amplifier is an electronic circuit that produces output that is proportional to the logarithm of the applied input. How to provide saturation current and temperature compensation in log-amp? View Answer, 2. Find the output voltage of the log-amp? c) Applying input and reference voltage to separate log-amps The nodal equation at the inverting input terminal’s node is −, $$=>I_{f}=\frac{V_i}{R_1}......Equation 1$$, The following is the equation for current flowing through a diode, when it is in forward bias −, $$I_{f}=I_{s} e^{(\frac{V_f}{nV_T})} ......Equation 2$$. Therefore, the op-amp based anti-logarithmic amplifier circuit discussed above will produce an output, which is proportional to the anti-natural logarithm (exponential) of the input voltage ${V_i}$ when, ${R_fI_s}= 1V$. $$=>V_{0}=-R_{f}I_{f}.........Equation 4$$, We know that the equation for the current flowing through a diode, when it is in forward bias, is as given below −, $$I_{f}=I_{s} e^{\left(\frac{V_f}{nV_T}\right)}$$, Substituting the value of $I_{f}$ in Equation 4, we get, $$V_{0}=-R_{f}\left \{{I_{s} e^{\left(\frac{V_f}{nV_T}\right)}}\right \}$$, $$V_{0}=-R_{f}{I_{s} e^{\left(\frac{V_f}{nV_T}\right)}}......Equation 5$$, The KVL equation at the input side of the inverting terminal of the op amp will be, Substituting, the value of in the Equation 5, we get −, $$V_{0}=-R_{f}{I_{s} e^{\left(\frac{V_i}{nV_T}\right)}}$$. Please note that these amplifiers fall under non-linear applications. d) VO = Vref-(10-k’vi) Negative voltages or currents can be first rectified and then applied to the log amp, but this adds the errors from the rectifier. exponential to the input voltage. The concepts of logarithm and exponential are used throughout mathematics. This is the Multiple Choice Questions in Special-Purpose Op-Amp Circuits from the book Electronic Devices – Electron Flow Version and Conventional Current Version 8th Edition by Thomas L. 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Note that, in the above equation the parameters n, ${V_T}$ and $I_{s}$ are constants. This current then feeds $$R_f$$, which produces the output voltage. The derivation of the input/output Equation is similar to the log … You are allowed to answer only once per question. Express log 4 (10) in terms of b.; Simplify without calculator: log 6 (216) + [ log(42) - log(6) ] / log(49) For example, if 24 = 16, then 4 is the logarithm of 16 with the base as 2. According to the virtual short concept, the voltage at the inverting input terminal of op-amp will be equal to the voltage present at its non-inverting input terminal. https://www.sanfoundry.com/linear-integrated-circuit-mcqs-log-antilog-amplifier \$\endgroup\$ – … a) VO = Vref/(10-k’vi) When we are solving some logarithm, any part can be unknown. So, the output voltage $V_{0}$ will be proportional to the natural logarithm of the input voltage $V_{i}$ for a fixed value of resistance $R_{1}$. View Answer, 3. Which of the following functions does the antilog computation required to perform continuously with log-amps? Floyd Self-test in Log and Antilog Amplifiers Floyd Self-test in Converters and Other Op-Amp Circuits If you are looking for the Multiple Choice Questions in Floyd’s Electronic Devices proceed to ➡️ Floyd: MCQ in Special-Purpose Op-Amp Circuits The log amp gives an indication of the instant-by-instant low-frequency changes in the envelope, or amplitude, of the signal in the log domain in the same way that a digital voltmeter, set to "ac volts", gives a steady (linear) reading when the input is connected to a constant amplitude sinewave and follows any adjustments to the amplitude. Multiple Choice Questions and Answers on Amplifiers with Negative Feedback. Join our social networks below and stay updated with latest contests, videos, internships and jobs! The circuit diagram of an op-amp based logarithmic amplifier is shown in the following figure −. In this article, we will see the different antilog amplifier circuits, its working and antilog amplifier applications. According to the virtual short concept, the voltage at the inverting input terminal of an op-amp will be equal to the voltage at its non-inverting input terminal. This goes into anti log amp U4. Participate in the Sanfoundry Certification contest to get free Certificate of Merit. An op-amp based anti-logarithmic amplifier produces a voltage at the output, which is proportional to the anti-logarithm of the voltage that is applied to the diode connected to its inverting terminal. log a 1 = 0 and log a a = 1. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground. We would like to show you a description here but the site won’t allow us. The operational amplifier circuit configurations which can perform mathematical operations such as log and antilog (exponential), including an amplification of the input signal provided to the circuit, are known as Logarithmic amplifier and Antilogarithmic amplifier respectively. Anti-logarithmic or exponential amplifier (or simply antilog amplifier) is an op-amp circuit configuration, whose output is proportional to the exponential value or anti-log value of the input. a) Applying reference voltage alone to two different log-amps © 2011-2021 Sanfoundry. View Answer, 6. All Rights Reserved. Output of summing amp U3 is 1.2V then. 9. a) 8.7v Therefore, the op-amp based logarithmic amplifier circuit discussed above will produce an output, which is proportional to the natural logarithm of the input voltage ${V_T}$, when ${R_1I_s}=1V$. Find the output voltage of the log-amplifier In order to crack any major entrance test, aspirants need to practice solving logarithm questions. An anti-logarithmic amplifier, or an anti-log amplifier, is an electronic circuit that produces an output that is proportional to the anti-logarithm of the applied input. This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. c) VO = Vref×(10-k’vi) A logarithm of a number is the power to which a given base must be raised to obtain that number. You may also like: Antilogarithmic Amplifier. Output : Natural logarithm of 14 is : 2.6390573296152584 Logarithm base 5 of 14 is : 1.6397385131955606 2. log2(a) : This function is used to compute the logarithm base 2 of a. Multiple Choice Questions and Answers on Op-Amp ( Operational Amplifier ) In addition to reading the questions and answers on my site, I would suggest you to check the following, on amazon, as well: Question Bank in Electronics & Communication Engineering by Prem R Chadha Displays more accurate result than log(a,2). Calculate the base voltage of Q2 transistor in the log-amp using two op-amps? To solve this problem, logarithm was invented in mathematics. They have numerous applications in electronics, such as: We can write it as 4 = log 2= 16. b) Applying input and reference voltage to same log-amps 7. From log a a = 1 we have that a 1 = a, which is true for any real number a. Applications of Anti-logarithmic Amplifier IC. •Log and Antilog Amplifiers are non-linear circuits in which the output voltage is proportional to the logarithm (or exponent) of the input. Time and Work Formula and Solved Problems. An antilog amplifier has a _____ in series with the input. From log a 1 = 0 we have that a 0 = 1, which is true for any real number a. Log and AntiLog Amplifiers Recommended Text: Pallas-Areny, R. & Webster, J.G., Analog Signal Processing, Wiley (1999) pp. 1. That means zero volts is applied at the non-inverting input terminal of the op-amp. Note that the transistor is used to turn the input voltage into an input current, with a log function. Find the circuit used for compensating dependency of temperature in the output voltage? d) 6.2v A current-to-voltage converter produces a A(n) ________ amplifier provides "a barrier" between the input and output for the protection of human life or sensitive equipment. Basics of Integrated Circuits Applications. View Answer, 8. In addition to reading the questions and answers on my site, I would suggest you to check the following, on amazon, as well: Question Bank in Electronics & Communication Engineering by Prem R Chadha If V in is the input signal applied to a Anti log amplifier then the output is V o = K * exp (a * V i) where K is proportionality constant, a is constant. So, the voltage at its inverting input terminal will be zero volts. View Answer, 7. D. 4. MCQ Exam ON : Special-Purpose Op-Amp Circuits . Time and Work Concepts. Observe that the output voltage ${V_0}$ is having a negative sign, which indicates that there exists a 1800 phase difference between the input and the output. a) 6.314(kT/q)v What are Exponents? The input voltage, 6v and reference voltage, 4 v are applied to a log-amp with saturation current and temperature compensation. Log-Antilog Log and antilog amp circuits include the same elements but arranged in different feedback configurations. shorthand/stand for the repeated multiplication of a variable Basically it performs mathematical operation of a logarithm. Questions on Logarithm and exponential with solutions, at the bottom of the page, are presented with detailed explanations.. The electronic circuits which perform the mathematical operations such as logarithm and anti-logarithm (exponential) with an amplification are called as Logarithmic amplifier and Anti-Logarithmic amplifier respectively. In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground. B. 1) ... What part of the characteristic curve of a diode is useful for log amplifiers? Determine the output voltage for the given circuit Solve the equation (1/2) 2x + 1 = 1 Solve x y m = y x 3 for m.; Given: log 8 (5) = b. AntiLog amplifier or anti–logarithmic amplifier is an electronic circuit that produces output that is proportional to the anti-logarithm of the applied input. c) 0.405(kT/q)v Find the circuit that is used to compress the dynamic range of a signal? It is well known that some processes such as multiplication and division, can be performed by addition and subtraction of logs. You can now earn points by answering the unanswered questions listed. Antilog amplifier does the exact opposite of a log amplifier. A logarithmic amplifier, or a log amplifier, is an electronic circuit that produces an output that is proportional to the logarithm of the applied input. If in the logarithm the base is 10, then instead of log 10 we write lg. https://www.theengineeringknowledge.com/log-and-antilog-amplifiers C. 10. 1. This section discusses about the op-amp based logarithmic amplifier in detail. Note that in the above equation, the parameters n, ${V_T}$ and $I_{s}$ are constants. The circuit diagram of an op-amp based anti-logarithmic amplifier is shown in the following figure −. Banking on our enriched industry experience, we are able to offer a wide gamut of Log and Antilog Amplifier.These high performing Log and Antilog Amplifiers offered by us are non-linear circuits, in which the output voltage is proportional to the logarithm (or exponent) of the input.We take into account the ever changing requirements of different industries and offer innovative range of products. d) None of the mentioned How much current would have to flow in diode-connected transistor Q4 for V+ to equal V- for U4? c) Sinh(x) It can be used direct db display on spectrum analyzer. Anti log amplifier is one which provides output proportional to the antilog i.e. A basic anti-log amplifier is shown in Figure $$\PageIndex{3}$$. So, the output voltage ${V_0}$ will be proportional to the anti-natural logarithm (exponential) of the input voltage ${V_i}$, for a fixed value of feedback resistance ${R_f}$. The KVL equation around the feedback loop of the op amp will be −, Substituting the value of $V_{f}$ in Equation 2, we get −, $$I_{f}=I_{s} e^{\left(\frac{-V_0}{nV_T}\right)} ......Equation 3$$, Observe that the left hand side terms of both equation 1 and equation 3 are same. In other words, if by = x then y is the logarithm of x to base b. b) VO = -(kT/q)×ln(Vi/Vref) d) VO = (kT/q)×ln(Vi/Vref) 293-321 I ntroduction Log and Antilog Amplifiers are non-linear circuits in which the output voltage is proportional to the logarithm (or exponent) of the input. • It is well known that some processes such as multiplication and division, can be performed by addition and subtraction of logs. Sanfoundry Global Education & Learning Series – Linear Integrated Circuits. Which of the following functions does the antilog computation required to perform continuously with log-amps? a) VO = -(kT)×ln(Vi/Vref) Introduction Log and Antilog Amplifiers are non-linear circuits in which the output voltage is proportional to the logarithm (or exponent) of the input. Hence, equate the right hand side term of those two equations as shown below −, $$\frac{V_i}{R_1}=I_{s}e^{\left(\frac{-V_0}{nV_T}\right)}$$, $$\frac{V_i}{R_1I_s}= e^{\left(\frac{-V_0}{nV_T}\right)}$$, Applying natural logarithm on both sides, we get −, $$In\left(\frac{V_i}{R_1I_s}\right)= \frac{-V_0}{nV_T}$$, $$V_{0}=-{nV_T}In\left(\frac{V_i}{R_1I_s}\right)$$. c) 3.3v If log 3 [log 2 (x 2 – 4x – 37)] = 1, where ‘x’ is a natural number, find the value of x. Answer Questions and Earn Points !!! Observe that the output voltage $V_{0}$ has a negative sign, which indicates that there exists a 1800 phase difference between the input and the output. Log Amplifier using a Single Diode and Op-Amp. 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That means zero volts is applied at the inverting input terminal of the op-amp based logarithmic is. Then applied to a log-amp with saturation current and temperature compensation computation required to perform continuously with log-amps series Linear! Other words, if by = x then y is the diode ’ s thermal equivalent voltage are for. With the input current and temperature compensation in log-amp is one which provides output proportional to the logarithm base! Answers on Amplifiers with Negative Feedback ’ t allow us used throughout mathematics of Linear circuits!, then 4 is the logarithm of x to base b a logarithm of to. Output proportional to the antilog computation required to perform continuously with log-amps questions and Answers perform with. Unanswered questions listed, but this adds the errors from the rectifier with detailed..... Using two op-amps Log-Antilog log and antilog amp circuits include the same elements but arranged different.