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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Documents Flashcards Grammar checker. It is well known that some processes such as ampoifiers 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 to the circuit must be small compared to R1. Omitting R1 yields a currentinput log amp.

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 ajtilog 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 antiolg.

### Log amplifier – Wikipedia

To investigate its stability, refer to the incremental model, where the BJT has been replaced by its common-base smallsignal model.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 ampljfiers 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. Alternatively, the log amp amplifieds 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 same 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.

## Log and AntiLog Amplifiers

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.

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 can be positive or negative. DIT offerings in year 3 and 4.

### Log and AntiLog Amplifiers

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