LOG AND ANTILOG AMPLIFIER PDF

Sazil 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. Since the non inverting terminal of opamp is at ground potential. Temperature compensation must correct both error sources. The source impedance of voltage signals applied to the circuit must be small compared to R1. It is obvious from the circuit shown above that negative feedback is provided from output to inverting terminal.

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IS] The output of the circuit is, thus, proportional to the log of the input voltage. However, the output is dependent on the saturation current which varies from transistor to transistor and also with temperature.

Compensation circuits can be added to stabilize the output against these variations. BACK TO TOP Anti-Logarithmic Amplifier or Exponential Amplifier Anti-logarithmic or exponential amplifier or simply antilog amplifier is an op-amp circuit configuration, whose output is proportional to the exponential value or anti-log value of the input. Antilog amplifier does the exact opposite of a log amplifier. Antilog amplifiers along with log amplifiers are used to perform analogue computations on the input signals.

The circuit of an antilog amplifier using op-amp is shown in the figure below. It is noted that by exchanging the positions of the transistor and the resistor, the log amplifier can be made to work as antilog amplifier.

The base-collector voltage of the transistor is maintained at ground potential, from the virtual ground concept. Compensating circuits can be added to stabilize the output against such variations. The current to voltage converter circuit is most commonly used to amplify the current output of photodiodes, photo-detectors, accelerometers and other sensor devices to a noticeable and usable voltage level.

A simple current-to-voltage converter circuit will have a feedback resistor, with a large value of resistance. The gain of the amplifier is dependent on this resistor. Depending on the application, a current-to-voltage converter can be constructed in different ways. All the configurations convert the low-level current output of a sensor device to a significant voltage level.

The gain and the bandwidth of the circuit changes with different types of sensors. The circuit of a basic current-to-voltage converter is shown in the figure above. The sensor device, in this case is a photo-diode, and it is connected to the inverting input terminal and the non-inverting input terminal is grounded.

This provides a low impedance load for the photo-diode, which keeps the voltage across the photo-diode low. The high gain of the op-amp keeps the photo-diode current, Ip, equal to the feedback current through resistor Rf. The input offset voltage due to the photo-diode is very low, since the photo-diode has no external bias. This provides a large output gain, without any output offset voltage. Rf The above equation satisfies only for the DC and low-frequency gain current-to-voltage converter.

If the gain is large, any input offset voltage at the non-inverting input of the op-amp will result in an output offset voltage. To minimize these effects, the current-to-voltage converters are usually designed with FETs at the op-amp input, which have very low input offset voltages. A positive-going signal at the input of an inverting amplifier would result in a negative-going signal at the output and vice versa. An AC sinusoidal signal at the input would produce o out of phase sinusoidal signal at the output.

Above figure shows the circuit of a typical inverting amplifier using an op-amp. The circuit uses a negative feedback connection, through the resistor Rf. The input signal is applied to the inverting input terminal and the non-inverting input terminal is grounded. Since the input current to the op-amp is ideally zero, the current I due to the input voltage flows through resistors R1 and Rf. A non-inverting amplifier uses a negative feedback connection, but instead of feeding the entire output signal to the input, only a part of the output signal voltage is fed back as input to the inverting input terminal of the op-amp.

Above figure shows a typical non-inverting amplifier. The input signal is applied to the non-inverting input terminal and the output is fed to the inverting input terminal through a resistive potential divider network. When a positive-going input signal is applied to the non-inverting input terminal, the output voltage will shift to keep the inverting input terminal equal to that of the input voltage applied.

The closed-loop voltage gain of a non-inverting amplifier is determined by the ratio of the resistors R1 and R2 used in the circuit. Practical non-inverting amplifiers will have a resistor in series with the input voltage source, to keep the input current equal in both input terminals. An op-amp can be used to perform various mathematical operations such as addition, subtraction, multiplication along with calculus operations like differentiation and integration.

Op-amps are used for a variety of applications such as AC and DC signal amplification, filters, oscillators, voltage regulators, comparators in most of the consumer and industrial devices. Today, op-amps are very popular building blocks in analogue electronic circuits.

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Log And Anti Log Amplifiers

IS] The output of the circuit is, thus, proportional to the log of the input voltage. However, the output is dependent on the saturation current which varies from transistor to transistor and also with temperature. Compensation circuits can be added to stabilize the output against these variations. BACK TO TOP Anti-Logarithmic Amplifier or Exponential Amplifier Anti-logarithmic or exponential amplifier or simply antilog amplifier is an op-amp circuit configuration, whose output is proportional to the exponential value or anti-log value of the input. Antilog amplifier does the exact opposite of a log amplifier. Antilog amplifiers along with log amplifiers are used to perform analogue computations on the input signals. The circuit of an antilog amplifier using op-amp is shown in the figure below.

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Operational Amplifier Applications

Log And Anti Log Amplifiers Advertisements Next Page 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. Please note that these amplifiers fall under non-linear applications. Logarithmic Amplifier A logarithmic amplifier, or a log amplifier, is an electronic circuit that produces an output that is proportional to the logarithm of the applied input. This section discusses about the op-amp based logarithmic amplifier in detail.

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