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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## logarthmic, anti logarthmic amplifiers

Leave a Reply Cancel reply Your email address will not be published. Logarithmic amplifier zntilog the output proportional to the logarithm of input signal.

According to the virtual short conceptthe voltage at the inverting input terminal of an op-amp will amplifiet equal to the voltage at its non-inverting input terminal. V is voltage applied across diode; V t is the voltage equivalent of temperature. The figure of anti-logarithmic amplifier using matched diode is shown in figure below. Applying KCL at inverting node of opamp we get. Complete Electrical Symbol 3. Your email address will not be published.

As we know that is very small. From the figure we can also conclude that transistor base emitter voltage V BE is equivalent input voltage V i i. This section discusses about the op-amp based logarithmic amplifier in detail. 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.

It is obvious from the circuit shown above that negative feedback is provided from output to inverting terminal. Observe that the left hand side terms of both equation 1 and equation 3 are same.

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

This section discusses about the op-amp based anti-logarithmic amplifier in detail. Gain of logarithmic amplifier. You can amplifirr with me on: Best Arduino Projects 2. I edit and author this site.

So, the voltage at its inverting input terminal will be zero volts. Project Using and 4. A logarithmic amplifieror a log amplifieris an electronic circuit that produces an output that is proportional to the logarithm of the applied input. Assuming both diode and matched thus material constant, thermal voltage of diode and saturation current of diode is also same.

So, the voltage at the inverting input terminal will be zero volts. Hence applying KCL at inverting terminal of opamp, we get. Gain of Anti log amplifier. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground.

Easy Electronic Projects 5. Electronic Game and Fun Projects. Thus we can write. This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. 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. Antilogarithmic amplifier is one whose output is antilogarithmic exponential of input. As we know that. The circuit arrangement for Antilogarithmic amplifier is illustrated in figure 1.

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. Please note that these amplifiers fall under non-linear applications.

The output is depending upon output current of transistor and feedback resistor. Since the non inverting terminal of opamp is at ground potential. Using the concept of virtual short between the input terminals of an opamp the voltage at inverting terminal will be zero volts.

In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground. The output voltage expression becomes. Now putting the value of collector current of transistor I C in equation 1. Anti log amplifier is one which provides ueing proportional to the anti log i.

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.

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. Assuming both transistors are matched. A simple Anti log amplifier is shown below. The logarithmic circuit can be redrawn as follows. Thus, we can write.

Google Plus and Facebook. If you have any comments or suggestions please use our contact page We strictly ignore emails regarding post helps or explanation of circuits and projects ; for those purpose please use our comment feature ; We will surely help you by replying to your comment; It may helps other too. Here a general purpose NPN transistor is connected to inverting input of op-amp. Two matched transistors is used here as shown in figure, where input is given to the non-inverting amplifier pin of first op-amplifier A1.

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. A resistor is connected in feedback path. Two matched diodes are used here, where one diode D 1 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.