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 output voltage expression becomes. Antilogarithmic amplifier is one whose output is antilogarithmic exponential of input. So, the voltage at the inverting input terminal will be zero volts. Assuming both diode and matched thus material constant, thermal voltage of diode and saturation current atnilog diode is also same. The output is depending upon output current of transistor and feedback resistor. This section discusses about the op-amp based logarithmic amplifier ampplifier detail.

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.

### logarthmic, anti logarthmic amplifiers | ECE Tutorials

I edit and author this site. Best Arduino Projects 2. The figure of anti-logarithm amplifier is shown in figure 3. 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. This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail.

Voltage at inverting pin of op-amp A1 is potentially equal to voltage at non-inverting input of op-amp i. A resistor is connected in ol path. Logarithmic amplifier operation The circuit diagram of logarithmic amplifier is as shown below logarithmic amplifier.

Your email address will not be published. Applying KCL at inverting node of opamp we get.

Now putting the value of collector current of transistor I C in equation 1. Since the non inverting terminal of opamp is at ground potential. 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.

Leave a Reply Cancel reply Your email address will not be published. As we know that. The circuit diagram of logarithmic amplifier is as shown below. 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.

Thus, thermal voltage of 1 st transistor will be same amllifier thermal voltage of 2 nd transistor and amlifier current of 1 st transistor will be equal to saturation current of 2 nd transistor. An op-amp based logarithmic amplifier produces a voltage at the output, which is proportional to the logarithm of the voltage applied to the resistor connected to its inverting terminal.

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

## Log And Anti Log Amplifiers

An anti-logarithmic amplifieror an anti-log amplifieris an electronic anrilog that produces an output that is proportional to the anti-logarithm of the applied input. It means zero volts is applied to its non-inverting input terminal. Please note that these amplifiers fall under non-linear applications. As we know that is very small. So, the voltage at its antiloog input terminal will be zero volts. 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.

Gain of Anti log amplifier. Assuming both transistors are matched. Anti log amplifier is one which provides output proportional to the anti log i. Applying Antilog on both sides we get.

You May Also Like. It is obvious from the circuit shown above that negative feedback is provided from output to inverting terminal.

### Antilogarithmic Amplifier | Derivation

Google Plus and Facebook. Hence applying KCL at inverting terminal of opamp, we get. Thus we can write. The logarithmic circuit can be redrawn as follows. The figure of anti-logarithmic amplifier using matched diode is shown in figure below.

You can connect with me on: 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.

Electronic Game and Fun Projects. The circuit arrangement for Antilogarithmic amplifier is illustrated in figure 1. The anti log amplifier can be redrawn as follows. Thus, we can write. Logarithmic amplifier gives the output proportional to the logarithm of input signal. That means zero volts is applied at the non-inverting input terminal of the op-amp.