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Introduction Log and Antilog Amplifiers are non-linear circuits in which the output voltage is proportional to the logarithm (or exponent) of the input. 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. 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.

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Hence applying KCL at inverting terminal of opamp, we get. The diode dynamic resistance also drops with rising log current until saturated where the bulk resistance limits the minimum resistance.

Temperature compensation can be achieved by anitlog same technique shown for log amps. By using this site, you agree to the Terms of Use and Privacy Policy.

You can help Wikipedia by expanding it. Anti log amplifier is one which provides antulog proportional to the anti log i.

Constant terms are omitted for simplicity. From Wikipedia, the free encyclopedia. It is well known that some processes such as multiplication and division, can be performed by addition and subtraction of logs.

logarthmic, anti logarthmic amplifiers

The anti log amplifier can be redrawn as follows. I know there is problem with the last stage, the last opamp should give me gain: It means zero volts is applied to its non-inverting input terminal.


Gain of logarithmic amplifier. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground. Then finally choose a max temp difference of the log and antilog diodes to avoid gain and offset errors. Using the concept of virtual short between amplufiers input terminals of an opamp the voltage at inverting terminal will be zero volts.

Unclear what you’re asking. Amplifieers up using Email and Password. Omitting R1 yields a currentinput log amp. Sign up or log in Sign up using Google. The final output is developed by an inverting amplifier with a voltage gain of —K2. The reverse saturation current for the diode doubles for every ten degree Celsius rise in temperature.

This section discusses about the op-amp based anti-logarithmic amplifier in detail. 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. Very similar question from a month ago: I’m trying to build an analog multiplier that takes any antilkg voltages and produces the product for them.

logarthmic, anti logarthmic amplifiers | ECE Tutorials

Hence, it is very difficult to set the reference voltage for the circuit. A log amplifier is an amplifier for which the output voltage V out is K times the natural log of the input voltage V in. The circuit diagram of logarithmic amplifier is as shown below.


Then determines the required input bias current and offset must be to achieve this. Post Your Answer Discard 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. So this is another tradeoff for diode size vs bandwidth vs temp rise.

The bulk size and Pd rating of the diode affects the thermal resistance and bulk resistance or ESR, and also junction capacitance and bandwidth.

Observe that the left hand side terms of both equation 1 and equation 3 are same. As such, they can vary over a wide range of values.

Log amplifier

Does this seem reasonable? That means zero volts is applied at the non-inverting input terminal antiog the op-amp. A logarithmic amplifieror a log amplifieris an electronic circuit that produces an output that is proportional to the logarithm of the applied input.

Please think about what you are doing in your simulation. Alternatively, the log amp can be preceded by a precision current inverter.