# ANTILOG AMPLIFIER USING OP AMP PDF

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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So, the voltage at the inverting input terminal will be zero volts. Applying Antilog on both sides we get. So, the voltage at its inverting input terminal will be antilkg volts.

From the figure we can also conclude that transistor base emitter voltage V BE is equivalent input voltage V i i. 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. Here a general purpose NPN transistor is connected to inverting input of op-amp. The figure of anti-logarithm amplifier is shown ol figure 3.

### Linear Integrated Circuits Applications Log And Anti Log Amplifiers

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This chapter discusses about the Usimg amplifier and Anti-Logarithmic amplifier in detail. This section discusses about the op-amp based logarithmic amplifier in detail. Project Using and 4. It is obvious from the circuit shown above that negative feedback is provided from output to inverting terminal.

Like logarithmic amplifierantilogarithmic is also a non-linear amplifier.

## Antilogarithmic Amplifier | Derivation

The output is depending upon output current of transistor and feedback resistor. This section discusses about the op-amp based anti-logarithmic amplifier in detail.

Easy Electronic Projects 5. Please note that these amplifiers fall under non-linear applications. An anti-logarithmic amplifieror an anti-log amplifieris an electronic circuit that produces an output that is proportional to the anti-logarithm of the applied input. Electronic Game and Fun Projects. 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.

A simple Anti log amplifier is shown below. 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.

Complete Electrical Symbol 3. Gain of logarithmic amplifier.

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.

usijg Assuming both diode and matched thus material constant, thermal voltage of diode and saturation current of diode is also same.

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Assuming both transistors are matched.

Applying KCL at inverting node of opamp we get. You can connect with me on: Thus we can write. The figure of anti-logarithmic amplifier using matched diode is shown in figure below. Using the concept of virtual short between the input terminals of an opamp the voltage at inverting terminal will be zero volts. Hence applying KCL at inverting terminal of opamp, we get. Thus, thermal voltage of ip 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.

Antilogarithmic amplifier is one whose output is antilogarithmic qmp of input. In the circuit shown above, the non-inverting input terminal of the op-amp is usiing to ground. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground. Now putting the value of collector current of transistor I C in equation 1.

That means zero volts is applied at the non-inverting input terminal of the op-amp. V is voltage applied across diode; V t is the voltage equivalent of temperature. As we know that. It means zero volts is applied to its non-inverting input terminal. Thus, we can write. The amplifie circuit can be redrawn as follows.