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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A resistor is connected in feedback path. Thus we can write. Anti log amplifier is one which provides output proportional to the anti log i. Applying KCL at inverting node of opamp we get. Using the concept of virtual short between qntilog input terminals of an opamp the voltage at inverting terminal will be zero volts.

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

The logarithmic circuit can antilob redrawn as follows.

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As we know that is very small.

## Log And Anti Log Amplifiers

V is voltage applied across diode; V t is the voltage equivalent of temperature. Electronic Game and Fun Projects. 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.

Google Plus and Facebook. Gain of logarithmic amplifier. Hence applying KCL at inverting terminal of opamp, we get. 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. 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.

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

Thus, we can write. Gain of Anti log amplifier. Your email address will not be published. As we know that.

Antilogarithmic amplifier is one whose output is antilogarithmic exponential of input. Project Using and 4.

Here a general purpose NPN transistor is connected to inverting input of amplifirr. It means zero volts is amplivier to its non-inverting input terminal. The output is depending upon output current of transistor and feedback resistor. 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.

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

An op-amp based anti-logarithmic amplifier produces a voltage at the output, which is aantilog to the anti-logarithm of the voltage that is applied to the diode connected to its inverting terminal. Thus, thermal voltage of 1 st transistor will be same to thermal sntilog of 2 nd transistor and saturation current of 1 st transistor will be equal to saturation current of 2 nd transistor. The circuit arrangement usiing Antilogarithmic amplifier is illustrated in figure 1. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground.

A simple Anti log amplifier is shown below. A logarithmic amplifieror a log amplifieris an electronic circuit that produces an output that is proportional to the logarithm of the applied input. Logarithmic amplifier gives the output proportional to the logarithm of input signal. 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.

### Antilogarithmic Amplifier | Derivation

The figure of anti-logarithmic amplifier using matched diode is shown in figure below. It is obvious from the circuit shown above that negative feedback is provided from output to inverting terminal.

Assuming both diode and matched thus material constant, thermal voltage of diode and saturation current of diode is also same. 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. The output voltage ip becomes.

## logarthmic, anti logarthmic amplifiers

So, the voltage at the inverting input terminal will be zero volts. Complete Electrical Symbol 3. This section discusses about the op-amp based anti-logarithmic amplifier in detail. Observe that the antilpg hand side terms of both equation 1 and equation 3 are same. I edit and author this site.

Now putting the value of collector current of transistor I C in equation 1. Easy Electronic Projects 5.