A logarithmic scale is a scale of measurement that uses the logarithm of a physical quantity instead of the quantity itself. It is used in conjunction with units such as with Bel which a logarithmic unit of measurement that expresses the magnitude of a physical quantity power or intensity relative to a specified or implied reference level. The Bel unit is quite large, instead we use decibel dB which is one-tenth of a Bel. That is not correct though, because to achieve a finer unit step we need to have a power ratio of show as ten steps. Thus we get the above equation.

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Sazil According to the virtual short conceptthe voltage at the inverting input terminal of an op-amp will be equal to the voltage at its non-inverting input terminal.

Since the non inverting terminal of opamp is at ground potential. Temperature compensation must correct both error sources. The source impedance of voltage signals applied to the circuit must be small compared to R1. It is obvious from the circuit shown above that negative feedback is provided from output to inverting terminal. So, the voltage at the inverting input terminal will be zero volts.

Please think about what you are doing in your simulation. 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.

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. Applying KCL at inverting node of opamp we get. The logarithmic circuit can be redrawn as follows. Figure next slide shows the use of a second, matched, transistor for offset compensation and a temperature-dependent gain for gain compensation. It means zero volts is ajd to its non-inverting input terminal.

Does this seem reasonable? It is well known that some processes such as multiplication and division, can be performed by addition and subtraction of logs. The electronic circuits which perform the mathematical operations such as logarithm and andd exponential with an amplification are called as Logarithmic amplifier and Anti-Logarithmic amplifier respectively.

Log and AntiLog Amplifiers Alternatively, the log amp can be preceded by a precision current inverter. Constant terms are omitted for simplicity. Sign up using Facebook. This relationship is shown in the following formula: Sign up or log in Sign up using Google. Post as a guest Name. Ziad Zmplifier this be used to perform division if you used a differential amplifier instead of a summing amplifier? But this depends on your thermal design.

The two output voltages from the log amplifiers are added and inverted by the unity-gain summing amplifier to produce the following result: Using a p-n-p transistor changes the polarity of input signals acceptable but limits the logarithmic range because of the degraded performance oog p-n-p transistors compared to n-p-n transistors www. SPICE simulation of voltage multiplier using log and antilog amplifier. Such circuit antioog are used in integrated log amps: In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground.

By summing the outputs of xntilog log amplifiers, you get the logarithm of the product of the two original input voltages. An anti-logarithmic amplifieror an anti-log amplifieris an electronic circuit that produces an output that is proportional to the anti-logarithm of the applied input.

Log-Antilog Log and antilog ampllifier circuits include the same elements but arranged in different feedback configurations. Please note that these amplifiers fall under non-linear applications. Using the concept of virtual short between the input terminals of an opamp the voltage at inverting terminal will be zero volts. Log And Anti Log Amplifiers It is called four-quadrant since inputs and output can be positive or negative.

Automated Classification of internet video content. Sign up using Email and Password. Then, by taking the antilogarithm, you get the product of the two input voltages as indicated in the following equations: Consider the voltage-input transdiode. Log and AntiLog Amplifiers The current inverter in Figure below uses two matched n-p-n transistors and a precision op amp to achieve accurate current inversion.

Omitting R1 yields a currentinput log amp. This section discusses about the op-amp based anti-logarithmic amplifier in detail. Negative voltages or currents can be first rectified and then applied to the log amp, but this adds the errors from the rectifier.

Home Questions Tags Users Unanswered. Company Table Recruiting Disciplines. D1 protects the base-emitter junction from excessive reverse voltages. So this is another tradeoff for diode size vs bandwidth vs temp rise. V is voltage applied across diode; V t is the voltage equivalent of temperature. TOP Related Posts.

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## LOG AND ANTILOG AMPLIFIER PDF

Log And Anti Log Amplifiers Advertisements Next Page 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. This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. Please note that these amplifiers fall under non-linear applications. Logarithmic 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. This section discusses about the op-amp based logarithmic amplifier in detail.

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## Log and Antilog Amplifiers

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