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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Ampliifer Flashcards Grammar checker. It is well known that some processes such as multiplication and division, can be performed by addition and subtraction of logs.

They have numerous applications in electronics, such as: The system bandwidth is narrower for small signals because emitter resistance increases for small currents. The source impedance of voltage signals applied antioog the circuit must be small compared to R1. Omitting R1 yields a currentinput log amp.

Log And Anti Log Amplifiers

Using a p-n-p transistor changes the polarity of input signals acceptable but limits the logarithmic range because of the degraded performance of p-n-p transistors compared to n-p-n transistors www. These basic circuits needs additional components to improove the overall performance, i.


Such circuit techniques are used in integrated log amps: IC log amps may cost about ten times the components needed to build a discrete-component log amp. Temperature compensation must correct both error sources. Figure next slide shows the use of a second, matched, transistor for offset compensation and a temperature-dependent gain for gain compensation. D1 protects the base-emitter junction from excessive reverse voltages.

Consider the voltage-input transdiode. To investigate its stability, refer to the incremental model, where the BJT has been replaced by its common-base smallsignal model. As such, they can vary over a wide range of values.

The analysis is the same as above for the transdiode connection, but the logarithmic range is limited to four or five decades because the base current adds to the collector current. Negative voltages or currents can be first rectified and then applied to the log amp, but this adds the errors from the rectifier.

logarthmic, anti logarthmic amplifiers

Alternatively, the log amp can be preceded by a precision current inverter. The current inverter in Figure below uses two matched n-p-n transistors and a precision op amp to achieve accurate current inversion. Antilog amps are used together with log amps to perform analog computation. Temperature compensation can be achieved by the antiog technique shown for log amps.


Log-Antilog Log and antilog amp circuits include the same elements but arranged in different feedback configurations. Some integrated log amps have uncommitted elements allowing us to implement antilog amps.

This relationship is shown in the following formula: To get the logarithm of a signal voltage use a Log amplifier. By summing the outputs of two log amplifiers, you get the logarithm of the product of the two original input voltages. Then, by taking the antilogarithm, you get the product of the two input voltages as indicated in the following equations: Constant terms are omitted for simplicity.

logarthmic, anti logarthmic amplifiers | ECE Tutorials

The two output voltages from the log amplifiers are added and inverted by the unity-gain summing amplifier to produce the following result: The final output is developed by an inverting amplifier with a voltage gain of —K2. It is called four-quadrant since inputs and output amplicier be positive or negative. DIT offerings in year 3 and 4. Company Table Recruiting Disciplines.

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