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 anti log amplifier can be redrawn as follows. It is obvious from the circuit shown usnig that negative feedback is provided from output to inverting terminal.

## Log And Anti Log Amplifiers

This section discusses about the op-amp based logarithmic amplifier in detail. Gain of logarithmic amplifier. You can connect with me on: The output voltage expression becomes.

The logarithmic circuit can be redrawn as follows. It means zero volts is applied to its non-inverting input terminal. Now putting the value of collector current of transistor I Amplifuer in equation 1. 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. Hence applying KCL at inverting terminal of opamp, we get.

A logarithmic amplifieror a log amplifieris an electronic circuit that produces an output that is proportional to the logarithm of the applied input. 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 zmplifier the diode connected to its inverting terminal. Complete Electrical Symbol 3. From the figure we can also conclude that transistor base emitter voltage V BE is equivalent input voltage V i i.

Antilogarithmic amplifier is one whose output is antilogarithmic exponential of input. The figure of anti-logarithm amplifier is shown in figure 3. The circuit arrangement for Antilogarithmic amplifier is illustrated in figure 1. V is voltage applied across diode; V t is the voltage equivalent of temperature. An op-amp based logarithmic amplifier produces a ueing at the output, which is proportional to the logarithm of the voltage applied to the resistor connected to its inverting terminal.

So, the voltage at the inverting input terminal will be zero volts. In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground. Best Arduino Projects 2. In the above circuit, the non-inverting input terminal of the op-amp is connected to ground.

That means zero volts is applied at the non-inverting input terminal of the 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. This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. Applying Antilog on both sides we get. As amplifker know that. Observe that the left hand side terms of both equation 1 and equation 3 are same.

A simple Anti log amplifier is shown below. Antilg, the voltage at its inverting input terminal will be zero volts. The figure of anti-logarithmic amplifier using matched diode is shown in figure below. Using the concept of virtual short between the input terminals of an opamp the voltage at inverting terminal will be zero volts.

Assuming both transistors are matched. Assuming both diode and matched thus material constant, thermal voltage of diode and saturation current of diode is also same. As we know that is very small. Two matched diodes are used here, where one diode D 1 is lp 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.

Thus, we can write. 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. 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. Please note that these amplifiers fall under non-linear applications.

The output is depending upon output current of transistor and feedback resistor. This section discusses about the op-amp based anti-logarithmic amplifier in detail. You May Also Like. 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. Google Amplifler and Facebook.

Since the non inverting terminal of opamp is at ground potential. Voltage at inverting pin of op-amp A1 is potentially equal to voltage at non-inverting input of op-amp i.

### logarthmic, anti logarthmic amplifiers | ECE Tutorials

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The circuit diagram of logarithmic amplifier is as shown below. Logarithmic amplifier operation The circuit diagram of logarithmic amplifier is as shown below logarithmic amplifier. Thus we can write. Logarithmic amplifier gives the output proportional to the logarithm of input signal.