1. We would like to show you a description here but the site won’t allow us. $V_{f}$ is the voltage drop across diode, when it is in forward bias. Basics of Integrated Circuits Applications. Find the circuit used for compensating dependency of temperature in the output voltage? Log amplifier or logarithmic amplifier is an electronic circuit that produces output that is proportional to the logarithm of the applied input. Here, y > 0, b > 0, and b ≠ 1. What are Exponents? 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 −, $$I_{f}=I_{s} e^{(\frac{V_f}{nV_T})} ......Equation 2$$. The power is sometimes called the exponent. Which of the following functions does the antilog computation required to perform continuously with log-amps? View Answer, 7. Answer & Explanation Most Popular Articles. b) 5.3v 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. Floyd. 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. Multiple Choice Questions and Answers on Amplifiers with Negative Feedback. Note that the transistor is used to turn the input voltage into an input current, with a log function. 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 In order to crack any major entrance test, aspirants need to practice solving logarithm questions. 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. The derivation of the input/output Equation is similar to the log … Time and Work Formula and Solved Problems. View Answer, 2. When we are solving some logarithm, any part can be unknown. This goes into anti log amp U4. 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. Which of the following functions does the antilog computation required to perform continuously with log-amps? c) 0.405(kT/q)v The electronic circuits which perform the mathematical operations such as logarithm and anti-logarithm (exponential) with an amplification are called as It can be used direct db display on spectrum analyzer. So, the voltage at its inverting input terminal will be zero volts. We can write it as 4 = log 2= 16. Note that in the above equation, the parameters n, ${V_T}$ and $I_{s}$ are constants. You can now earn points by answering the unanswered questions listed. If you are looking for a reviewer in Electronics Engineering this will definitely help. This current then feeds \(R_f\), which produces the output voltage. a) VO = -(kT)×ln(Vi/Vref) A logarithm of a number is the power to which a given base must be raised to obtain that number. d) 1.214(kT/q)v c) VO = -(kT/q)×ln(Vref/Vi) Participate in the Sanfoundry Certification contest to get free Certificate of Merit. In other words, if by = x then y is the logarithm of x to base b. c) 3.3v Log and AntiLog Amplifiers Recommended Text: Pallas-Areny, R. & Webster, J.G., Analog Signal Processing, Wiley (1999) pp. shorthand/stand for the repeated multiplication of a variable 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. $$=>V_{0}=-R_{f}I_{f}.........Equation 4$$, 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 −, $$V_{0}=-R_{f}{I_{s} e^{\left(\frac{V_i}{nV_T}\right)}}$$. Log-Antilog Log and antilog amp circuits include the same elements but arranged in different feedback configurations. This set of Linear Integrated Circuit Multiple Choice Questions & Answers (MCQs) focuses on “Log and Antilog 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. c) Sinh(x) If log 3 [log 2 (x 2 – 4x – 37)] = 1, where ‘x’ is a natural number, find the value of x. 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 In this article, we will see the different log amplifier circuits, its working and log amplifier applications. 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 ${R_1I_s}=1V$. \$\endgroup\$ – … This section discusses about the op-amp based anti-logarithmic amplifier in detail. $V_{T}$ is the diode’s thermal equivalent voltage. View Answer, 5. Applications of Anti-logarithmic Amplifier IC. 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 $R_{1}$. To practice all areas of Linear Integrated Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers. For example, if 24 = 16, then 4 is the logarithm of 16 with the base as 2. Please note that these amplifiers fall under non-linear applications. The concepts of logarithm and exponential are used throughout mathematics. AntiLog amplifier or anti–logarithmic amplifier is an electronic circuit that produces output that is proportional to the anti-logarithm of the applied input. https://www.theengineeringknowledge.com/log-and-antilog-amplifiers Solve the equation (1/2) 2x + 1 = 1 Solve x y m = y x 3 for m.; Given: log 8 (5) = b. Express log 4 (10) in terms of b.; Simplify without calculator: log 6 (216) + [ log(42) - log(6) ] / log(49) In this article, we will see the different antilog amplifier circuits, its working and antilog amplifier applications. In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground. 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. Find the output voltage of the log-amp? 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. d) All of the mentioned C. 10. 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 −, $$In\left(\frac{V_i}{R_1I_s}\right)= \frac{-V_0}{nV_T}$$, $$V_{0}=-{nV_T}In\left(\frac{V_i}{R_1I_s}\right)$$. a) 6.314(kT/q)v log a 1 = 0 and log a a = 1. a) VO = Vref/(10-k’vi) b) log(x) 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. It means zero volts is applied to its non-inverting input terminal. Note that, in the above equation the parameters n, ${V_T}$ and $I_{s}$ are constants. 9. 7. Find the circuit that is used to compress the dynamic range of a signal? Output of summing amp U3 is 1.2V then. Time and Work Concepts. Figure 2: Anti-logarithmic Amplifier IC with antilog element in input. 1) ... What part of the characteristic curve of a diode is useful for log amplifiers? exponential to the input voltage. View Answer, 4. You may also like: Antilogarithmic Amplifier. View Answer. https://www.sanfoundry.com/linear-integrated-circuit-mcqs-log-antilog-amplifier •Log and Antilog Amplifiers are non-linear circuits in which the output voltage is proportional to the logarithm (or exponent) of the input. Introduction Log and Antilog Amplifiers are non-linear circuits in which the output voltage is proportional to the logarithm (or exponent) of the input. a) Applying reference voltage alone to two different log-amps They have numerous applications in electronics, such as: From log a a = 1 we have that a 1 = a, which is true for any real number a. The input voltage, 6v and reference voltage, 4 v are applied to a log-amp with saturation current and temperature compensation. 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. Determine the output voltage for the given circuit 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. 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, ${R_fI_s}= 1V$. A. 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. 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. Questions on Logarithm and exponential with solutions, at the bottom of the page, are presented with detailed explanations.. 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. If in the logarithm the base is 10, then instead of log 10 we write lg. D. 4. a) In(x) It is a non-linear amplifier used for amplification or compression of wide range of input signal for better resolution. Log Amplifier using a Single Diode and Op-Amp. b) VO = Vref+(10-k’vi) b) Applying input and reference voltage to same log-amps © 2011-2021 Sanfoundry. c) VO = Vref×(10-k’vi) Anti log amplifier is one which provides output proportional to the antilog i.e. Log and Antilog Amplifier. a) 8.7v An antilog amplifier has a _____ in series with the input. It is well known that some processes such as multiplication and division, can be performed by addition and subtraction of logs. From log a 1 = 0 we have that a 0 = 1, which is true for any real number a. Antilog amplifier does the exact opposite of a log amplifier. An antilog amplifier has a _____ in series with the input. View Answer, 8. That means zero volts is applied at the non-inverting input terminal of the op-amp. d) VO = Vref-(10-k’vi) 1. d) 6.2v How to provide saturation current and temperature compensation in log-amp? d) None of the mentioned 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 −. You are allowed to answer only once per question. • It is well known that some processes such as multiplication and division, can be performed by addition and subtraction of logs. b) VO = -(kT/q)×ln(Vi/Vref) Find the output voltage of the log-amplifier 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. 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. 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. The circuit diagram of an op-amp based anti-logarithmic amplifier is shown in the following figure −. 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. To solve this problem, logarithm was invented in mathematics. MCQ Exam ON : Special-Purpose Op-Amp Circuits . Answer Questions and Earn Points !!! 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. d) VO = (kT/q)×ln(Vi/Vref) Basically it performs mathematical operation of an anti-logarithm. 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 logarithmic amplifier in detail. Basically it performs mathematical operation of a logarithm. All Rights Reserved. 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 here is complete set of 1000+ Multiple Choice Questions and Answers, Prev - Linear Integrated Circuit Questions and Answers – Very High Input Impedance Circuit, Next - Linear Integrated Circuit Questions and Answers – Multiplier and Divider – 1, Linear Integrated Circuit Questions and Answers – Very High Input Impedance Circuit, Linear Integrated Circuit Questions and Answers – Multiplier and Divider – 1, Chemical Engineering Questions and Answers, Electrical Measurements Questions and Answers, Instrumentation Transducers Questions and Answers, Design of Electrical Machines Questions and Answers, Electrical Machines Questions and Answers, Wireless & Mobile Communications Questions & Answers, Electronic Devices and Circuits Questions and Answers, Basic Electrical Engineering Questions and Answers, Linear Integrated Circuits Questions and Answers, Linear Integrated Circuit Questions and Answers – Input Bias Current, Linear Integrated Circuit Questions and Answers – Basic DAC Techniques – 2, Linear Integrated Circuit Questions and Answers – Input Offset Current and Total Output Offset Voltage, Linear Integrated Circuit Questions and Answers – Instrumentation Amplifier – 2, Linear Integrated Circuit Questions and Answers – Peak Detector, Sampling & Hold Circuit and Absolute Value Output Circuit. View Answer, 6. Displays more accurate result than log(a,2). 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. Calculate the base voltage of Q2 transistor in the log-amp using two op-amps? 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. View Answer, 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 ${R_f}$. Sanfoundry Global Education & Learning Series – Linear Integrated Circuits. This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. c) Applying input and reference voltage to separate log-amps $I_{s}$ is the saturation current of the diode. So, the voltage at the inverting input terminal will be zero volts. How much current would have to flow in diode-connected transistor Q4 for V+ to equal V- for U4? In the above circuit, the non-inverting input terminal of the op-amp is connected to ground. B. b) 0.597(kT/q)v Negative voltages or currents can be first rectified and then applied to the log amp, but this adds the errors from the rectifier. A basic anti-log amplifier is shown in Figure \(\PageIndex{3}\).

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