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 logarithmic circuit can be redrawn as follows. From the figure we can also conclude that transistor base emitter voltage V BE is equivalent input voltage V i i. A logarithmic amplifieror a log amplifieris an electronic circuit that produces an output that is proportional to natilog logarithm of the applied input.

V is voltage applied across diode; V t is the voltage equivalent of temperature. Electronic Game and Fun Projects. Complete Electrical Symbol 3. In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground. As we know that. The figure of anti-logarithmic amplifier using matched diode is shown in figure below. Applying Antilog on both sides we get.

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. Best Arduino Projects 2.

### Antilogarithmic Amplifier | Derivation

That means zero volts is applied at the non-inverting input terminal of the op-amp. Using the concept of virtual zmplifier between the input terminals of an opamp the voltage at inverting terminal will be zero volts. Voltage at inverting pin of op-amp A1 is potentially equal to voltage at non-inverting input of op-amp i.

Since the non inverting terminal of opamp is at ground potential.

## Log And Anti Log Amplifiers

Here a general purpose NPN transistor is connected to inverting input of op-amp. Thus, we can write.

Assuming both transistors are matched. Project Using and 4. 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. Anyilog putting the value of collector current of transistor I C in equation 1.

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.

Your email address will not be published. You May Also Like. You can connect with me on: Observe that the left hand side terms of both equation 1 and equation 3 are same. Google Plus and Facebook. The circuit arrangement for Antilogarithmic amplifier is illustrated in figure 1.

### logarthmic, anti logarthmic amplifiers | ECE Tutorials

The anti log amplifier can be redrawn as follows. Gain of Anti log amplifier.

This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. Applying KCL at inverting node of opamp we get. This section discusses about the op-amp based logarithmic amplifier in detail.

The figure of anti-logarithm amplifier is shown in figure 3. Like logarithmic amplifierantilogarithmic is also a non-linear amplifier.

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.