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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Gain of Anti log amplifier. Now putting the value of collector current of transistor I C in equation 1. Thus we can write.

### Antilogarithmic Amplifier | Derivation

A resistor is connected in feedback path. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground. The electronic circuits which perform the mathematical operations such as logarithm and amplufier exponential with an amplification are called as Logarithmic amplifier and Anti-Logarithmic amplifier respectively.

This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. The output is depending upon output current of transistor and feedback resistor. Logarithmic amplifier gives the output proportional to the logarithm of input signal. That means zero volts is applied at the amplifiee input terminal of the op-amp.

Your email address will not be published. Leave a Reply Cancel reply Your email xmplifier will not be published. The logarithmic circuit can be redrawn as follows.

As we know amplifiee. 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 of the applied input. 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.

Assuming both diode and matched thus material constant, thermal voltage of diode and saturation current of diode is also same. Observe that the left hand side terms of both equation 1 and equation 3 are same. Anti log amplifier is one which provides output proportional to the anti log i.

Applying KCL at inverting node of opamp we get. The figure of anti-logarithmic amplifier using matched diode is shown in figure below.

From the figure we can also conclude that transistor base emitter voltage V BE is equivalent input voltage V i i. Electronic Game and Fun Projects. Assuming both transistors are matched. Project Using and 4. As we know that is very small.

Google Plus and Facebook. A simple Anti log amplifier is shown below. Thus, we can write. 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.

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. Two matched transistors is used hsing as shown in figure, where input is given to the non-inverting amplifier pin of first op-amplifier A1. Gain of logarithmic amplifier. 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.

The circuit diagram of logarithmic amplifier is as shown below.

Since the non inverting terminal of opamp is at ground potential. 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. A logarithmic amplifieror a log amplifieris an electronic circuit that produces an output that is proportional to the logarithm of the applied input.

This section discusses about the op-amp based anti-logarithmic amplifier in detail.

In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground. I edit and author this site.

## logarthmic, anti logarthmic amplifiers

This section discusses about the op-amp based logarithmic amplifier in detail. 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 antillg help you by replying to your comment; It may helps other too.

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