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. Company Table Recruiting Disciplines. Applying KCL antiloy inverting node of opamp we get.

It is obvious from the circuit shown above that negative feedback is provided from output to inverting terminal.

Log And Anti Log Amplifiers

Anti log amplifier is one which provides output proportional to the anti log i. 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. This relationship is shown in the following formula: Figure next slide shows the use of a second, matched, transistor for offset compensation and a temperature-dependent gain for gain compensation.

V is voltage applied across diode; V t is the voltage equivalent of temperature. The bulk size and Pd rating of the diode affects the thermal resistance and bulk resistance or ESR, and also junction capacitance and bandwidth.

Then determines the required input bias current and offset must be to achieve this.

The analysis is the same as above for the transdiode connection, but the logarithmic range anrilog limited to four or five decades because the base current adds to the collector current. Ziad Could this be used to perform division if you used a differential amplifier instead of a summing amplifier? Temperature compensation must correct both error sources. The two output voltages from the log amplifiers are added and inverted by the unity-gain summing amplifier to produce the following result: SPICE simulation of voltage multiplier using log and antilog amplifier.


This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. Using the concept of virtual short between the input terminals of an opamp the voltage at inverting terminal will be zero antilov. IC log amps may cost about ten times the components needed to build a discrete-component ampllifier amp. This is the basic layout of the circuit: Regression-based Active Learning for Fraud Detection.

Logarithmic amplifier operation The circuit diagram of logarithmic amplifier is as shown below logarithmic amplifier.

You’ve simulated it, so why do you ask if it works for you? Does this seem reasonable? Sign up or log in Sign up using Google. Tony EE rocketscientist 62k 2 21 A simple Anti log qmplifier is shown below. Some integrated log amps have lig elements allowing us to implement antilog amps. 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.

Documents Flashcards Grammar checker. Unclear what you’re asking. The electronic circuits which perform amplifir mathematical operations such as logarithm and anti-logarithm exponential with wntilog amplification are called as Logarithmic amplifier and Anti-Logarithmic amplifier respectively.

That means zero volts is applied at the non-inverting input terminal of the op-amp. Matched temperature by thermal coupling is desired or minimize self heating for low T rise.

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. The diode dynamic resistance also drops with rising log current until saturated where the bulk resistance limits the minimum resistance.

Log-Antilog Log and antilog amp circuits include the same elements but arranged in different feedback configurations. Post as a guest Name. Logarithmic amplifier gives the output proportional to the logarithm of input signal. The circuit diagram of logarithmic amplifier is as shown below. As such, they can vary over a wide range of values. The final output is developed by an inverting amplifier with a voltage gain of —K2.


Temperature compensation can be achieved by the same technique shown for log amps. To investigate its stability, refer to the incremental model, where the BJT has been replaced by its common-base smallsignal model. 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.

To get the logarithm of a signal voltage use a Log amplifier. A logarithmic amplifieror a log amplifieris an electronic circuit that produces an output that is proportional to the logarithm of the applied input.

Log and AntiLog Amplifiers

The K values control the R value which controls the diode amplifiet which can lead to errors if there is self heating which is the NTC Shockley Effect. Sign up using Email and Password. By summing the outputs of two log amplifiers, you get the logarithm of the product of the two original input voltages. 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.

Please think about what you are doing in your simulation. Then verify your design specs with sweeping voltages on the inputs and compute the gain and offset errors vs input.

You have 4 volts and 5 volts as your inputs. Since the non inverting terminal of opamp is at ground potential.