Antilog amplifiers along with log amplifiers are used to perform analogue computations on the input signals. The circuit of an antilog amplifier. But if diode current is too low then the OP Amp input offsets become Then finally choose a max temp difference of the log and antilog diodes. EXPERIMENT 8: Log and Antilog Amplifiers. Objectives: To understand the behavior of logarithmic and antilogarithmic amplifiers. Materials and Equipment.

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Applying Antilog on both sides we get.

But this depends on your thermal design. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

To get the logarithm of a signal voltage use a Log amplifier. A simple Antilov log amplifier is shown below. These basic circuits needs additional components to improove the overall performance, i.

Gain of Anti log amplifier. The two output voltages from the log amplifiers are added and inverted by the unity-gain summing amplifier to produce the following result: It is called akplifier since inputs and output can be positive or negative. Omitting R1 yields a currentinput log amp.

So, the voltage at its inverting input terminal will be zero volts. According to the virtual short conceptthe voltage at the inverting input terminal of amplkfier op-amp will be equal to the voltage at its non-inverting input terminal.


But if diode current is too low then the OP Amp input offsets become significant compared the the log1, log2 outputs. Sign up or log in Sign up using Google.

D1 protects the base-emitter junction from excessive reverse voltages. Ampliifer KCL at inverting node of opamp we get.

Log and AntiLog Amplifiers

Unclear what you’re asking. That means zero volts is applied at the non-inverting input terminal of the op-amp.

This section discusses about the op-amp based anti-logarithmic amplifier in detail. Then verify your design specs with sweeping voltages on the inputs and compute the gain and offset errors vs input.

Log And Anti Log Amplifiers

Email Required, but never shown. The diode dynamic resistance also drops with rising log current until saturated where the bulk resistance limits the minimum resistance.

The system bandwidth is narrower for small signals because emitter resistance increases for small currents. Home Questions Tags Users Unanswered.

This section discusses about the op-amp based amplifer amplifier in detail.

logarthmic, anti logarthmic amplifiers | ECE Tutorials

By summing the outputs of two log amplifiers, you get the logarithm of the product of the two original input voltages. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground. The circuit diagram of logarithmic amplifier is as shown below. By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies.

Such circuit techniques are used in integrated log amps: Very similar question from a month ago: In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground. Observe that the left hand side terms of both equation 1 and equation 3 are same. So this is another tradeoff for diode size vs bandwidth vs temp rise. The logarithmic circuit can be redrawn as follows. An op-amp based anti-logarithmic amplifier produces a voltage at the output, which is proportional to the ajplifier of the voltage that is applied to the diode connected to its inverting terminal.


Using the concept of virtual short between the input terminals of an opamp the voltage at inverting terminal will be zero volts. Akplifier electronic circuits which perform the mathematical operations such as logarithm and anti-logarithm exponential with an amplification are called as Logarithmic amllifier and Anti-Logarithmic amplifier respectively. IC log amps may cost about ten times the components needed to build a discrete-component log amp. Your email address will not be published.

Logarithmic amplifier operation The circuit diagram of logarithmic amplifier is as shown below logarithmic amplifier. Negative voltages or currents can be first rectified and then applied to the log amp, but this adds the errors from the rectifier. Hence applying KCL at inverting terminal of opamp, we get.