# 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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The circuit arrangement for Antilogarithmic amplifier is illustrated in figure 1. In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground.

V is voltage applied across diode; V t is the voltage equivalent of temperature. Voltage at inverting usin of op-amp A1 is potentially equal to voltage at non-inverting input of op-amp i. Logarithmic amplifier operation The circuit diagram of logarithmic amplifier is as shown below logarithmic amplifier. This section discusses about the op-amp based anti-logarithmic amplifier in detail.

Easy Electronic Projects 5. Applying KCL at inverting node of opamp we get. The logarithmic circuit can be redrawn as follows.

Best Arduino Projects 2. Please note that these amplifiers fall under non-linear applications. 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 wntilog current of 2 nd transistor.

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. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground.

The figure of anti-logarithm amplifier is shown in figure 3.

Assuming both diode and matched thus material constant, thermal voltage of diode and saturation current of diode is also same. Antilogarithmic amplifier is one whose output is antilogarithmic exponential of input.

So, the voltage at the inverting input terminal will be zero volts. A simple Anti log amplifier is shown below. Anti log amplifier is one which provides output proportional to the anti log i.

This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. Logarithmic amplifier gives the output proportional to the logarithm of input signal.

Applying Antilog on both sides we get. The circuit diagram of logarithmic amplifier is as shown below. You May Also Like.

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

Like logarithmic amplifierantilogarithmic is also a non-linear amplifier. 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. So, the voltage at its inverting input terminal will be zero volts. As we know that. According to the virtual short conceptthe voltage amlpifier the inverting input terminal of an op-amp will be equal to the voltage at its non-inverting input terminal.

Thus we can write.

## Log And Anti Log Amplifiers

You can connect with me on: A resistor is connected ampliier feedback path. Google Plus and Facebook. From the figure we can also conclude zmp transistor base emitter voltage V BE is equivalent input voltage V ap i. I edit and author this site. As we know that is very small.

Using the concept of virtual short between the input terminals of an opamp the voltage at inverting terminal will be zero volts. Thus, we can write. It is obvious from the circuit shown above that negative feedback is provided from output to inverting terminal. The figure of anti-logarithmic amplifier using matched diode is shown in figure below.

Hence applying KCL at inverting terminal of opamp, we get. Assuming both transistors are matched. Observe that the left hand side terms of both equation 1 and equation 3 are same. The anti log amplifier can be redrawn as follows.