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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### Antilogarithmic Amplifier | Derivation

This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. 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.

Leave a Reply Cancel reply Your email address will not be published. Google Plus and Facebook. Applying Antilog on both sides we get. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground. An op-amp based logarithmic amplifier produces a voltage at the output, which is a,plifier to the logarithm of the voltage applied to the resistor connected to its inverting terminal. Amlpifier can connect with me on: If you have any comments or suggestions please use our contact page We strictly ignore emails regarding post helps or explanation of circuits and amplirier ; for those purpose please use our comment feature ; We will surely help you by replying to your comment; It may helps other too.

That means zero volts is applied at the non-inverting input terminal of the antilof.

In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground. Here a general purpose NPN transistor is connected to inverting input of ampkifier. Your email address will not be published.

A simple Anti log amplifier is shown below. 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.

Easy Electronic Projects 5. The figure of anti-logarithm amplifier is shown in figure 3. Thus we can write. So, the voltage at its inverting input terminal will be zero volts.

Usijg 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. Voltage at inverting pin of op-amp A1 is potentially equal to voltage at non-inverting input of op-amp i.

Assuming both transistors are matched. Project Using and 4. 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. It is obvious from the circuit shown above that negative feedback is provided from output to inverting terminal.

Hence applying KCL at inverting terminal of opamp, we get.

## Antilogarithmic Amplifier | Derivation

A resistor is connected in feedback path. Please note that these amplifiers fall under non-linear applications. The output is depending upon output current of transistor and feedback resistor. Using the concept of virtual short between the input terminals of an opamp the voltage at inverting terminal will be zero volts. It means zero volts is applied to its non-inverting input terminal. This section discusses about the op-amp based logarithmic amplifier in detail.

From the figure we can also conclude that transistor base emitter voltage V BE is equivalent input voltage V i i. The output voltage expression becomes. Like logarithmic amplifierantilogarithmic is also a non-linear amplifier.

## logarthmic, anti logarthmic amplifiers

Anti log amplifier is one which provides output proportional to the anti log i. Applying KCL at inverting node of opamp we get. As we know that is very small. Antilogarithmic amplifier is one whose output is antilogarithmic exponential of input. Gain of Anti log amplifier. Observe that the left hand side terms of both equation 1 and equation 3 are same. Gain of logarithmic amplifier. Since the non inverting terminal of opamp is at ground potential.

So, the voltage at the inverting input terminal will be zero volts. As we know that. The circuit arrangement for Antilogarithmic amplifier is illustrated in figure 1.