a diode used in the feedback loop of an operational amplifier is forward biased by a constant current loop of an op-amp. Antilog is inverse operation of log operation so; antilog amplifiers can be operation. Log Amplifier using Diode. Fig 1. Antilogarithmic Amplifier using Single Transistor. The circuit Here a general purpose NPN transistor is connected to inverting input of op-amp. Basic Antilog Amplifier Using Diode The circuit diagram of basic antilog amplifier using diode As op-amp input current is zero, the current I must be same as If.

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This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. I edit and author this site. The output voltage expression becomes.

Since the non anyilog terminal of opamp is at ground potential. Logarithmic amplifier operation The circuit diagram of logarithmic amplifier is as shown below logarithmic amplifier.

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It means zero volts is applied to its non-inverting input terminal. From the figure we can also conclude that transistor base emitter voltage V BE is equivalent input voltage V i i. It is obvious from the circuit shown above that negative feedback is provided from output to inverting terminal.

## logarthmic, anti logarthmic amplifiers

Assuming both diode and matched thus material constant, thermal voltage of diode and saturation current of diode is also same. According to the virtual short conceptthe voltage at the inverting input terminal of op-amp will be equal to the voltage present at its non-inverting input terminal. Using the concept of virtual short usnig the input terminals of an opamp the voltage at inverting terminal will be zero volts.

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. A simple Anti log amplifier is shown below. The output is depending upon output current of transistor and feedback resistor. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground.

### Antilogarithmic Amplifier | Derivation

Complete Electrical Symbol 3. Electronic Game and Fun Projects. Assuming both transistors are matched. Google Plus and Facebook. Two matched diodes are used here, where one diode D abtilog is connected in feedback path and second diode D 2 is connected to inverting input of op-amp A2 in reverse bias mood as shown in figure 2.

This section discusses about the op-amp based anti-logarithmic amplifier in detail. Antilogarithmic amplifier is one whose output is antilogarithmic exponential of input.

An anti-logarithmic amplifieror an anti-log amplifieris an electronic circuit that produces an output that is proportional to the anti-logarithm anp the applied input. In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground.

The circuit diagram of logarithmic amplifier is as shown below. As we know that is very small. Best Arduino Projects 2. According to the virtual short conceptthe voltage at the inverting input terminal of an op-amp will be equal to the voltage at its non-inverting input terminal.

### logarthmic, anti logarthmic amplifiers | ECE Tutorials

You May Also Like. Hence applying KCL at inverting terminal of opamp, we get. The figure of anti-logarithm amplifier is shown in figure 3. As we know that. Here a general purpose NPN transistor is connected to inverting input of op-amp. Thus, thermal voltage of 1 st transistor will be same to thermal voltage of 2 nd transistor and saturation current of 1 st transistor will be equal to saturation current of 2 nd transistor. Your email address will not be published. The electronic circuits which perform the mathematical operations such as logarithm and anti-logarithm exponential with an amplification are called as Logarithmic amplifier and Anti-Logarithmic amplifier respectively.

Now putting the value of collector current of transistor I C in equation 1.

## Antilogarithmic Amplifier | Derivation

So, the voltage at its inverting input terminal will be zero volts. Observe that the left hand side terms of both equation 1 and equation 3 are same. Thus we can write. This section discusses about the op-amp based logarithmic amplifier in detail. The anti log amplifier can be redrawn as follows. So, the voltage at the inverting input terminal will be usign volts. Thus, we can write. Please note that these amplifiers fall under non-linear applications.

Project Using and 4. The logarithmic circuit can be redrawn as follows. Anti log amplifier is one which provides output proportional to the anti log i.

You can connect with me on: Applying KCL at inverting node of opamp we get. Like logarithmic amplifierantilogarithmic is also a non-linear ammplifier.

The figure of anti-logarithmic amplifier using matched diode is shown in figure below. Easy Electronic Projects 5. Voltage at inverting pin of op-amp A1 is potentially equal to voltage at non-inverting input of op-amp i.