An antilogarithmic amplifier, or an anti log amplifier, is an electronic circuit that produces an output that is proportional to the antilogarithm of the applied input. I would really appreciate some help with this problem. Functional black diagram principle of operation the antilog element converts the, although offset voltage of the antilog circuit may be balanced by connecting it in the log mode, and using, compensated antilog element, and a low bias current fet amplifier. There are three basic architectures which may be used to produce log amps. Anti log amplifier is one which provides output proportional to the antilog i. The circuit diagram of basic antilog amplifier using diode is shown in the fig. Antilog amplifier does the exact opposite of a log amplifier. Basic log circuit with feedback stability and transistor protection. Log and antilog amplifiers are nonlinear circuits in which the output voltage is proportional to the logarithm or exponent of the input. Basic antilog amplifier using diode the circuit diagram of basic antilog. In transmitters, log amps are also used to measure and regulate transmitted power. One operation can be that, these log and antilog amps can be used for making multipliers. Note that if you put in 0v, then you would have zero current through the diode and,ideally, 0v at the output. But if diode current is too low then the op amp input offsets become then finally.
Spice simulation of voltage multiplier using log and. Although logarithmic the output has the wrong sign for strict correctness. When working with a log amplifier that uses a diode as the log element, things get more complicated even than the math. The first stage takes the natural log of two inputs, which is summed by the inverting adder in the second stage, inverted using a unity gain inverting stage, and finally sent to an antilog stage to get the product of two signals. Pdf log and antilog amplifiers chandreyee mukherjee. The positions of diode and resistance are exchanged as compared to log amplifier circuit. Examples of integratedcircuit log and antilog amplifiers are the lcl 8048 log and lel 8049 antilog amplifiers. This variant is for processing negative input voltage and the output is a positive voltage.
Nevertheless, it is quite important not to forget the sign of the signal. Log and antilog are important circuits in what is called analog multiplicationcomputation. How to derive a logantilog opamp square law transfer. This section discusses about the op amp based anti logarithmic amplifier in detail.
Since the non inverting terminal of opamp is at ground potential. Logarithmic amplifier gives the output proportional to the logarithm of input signal. I found a worksheet online with an example of a square law circuit built using logantilog operational amplifiers. A log amplifier is commonly used to compress a signals largeamplitude dynamic range into something more manageable by other circuits such as adcs. To illustrate the input voltage to output voltage characteristics of the diode log amplifier the circuit of figure 7. The following topics have been covered in this video. I have no problem with the temperaturedependency of the configuration and so am trying to. In the antilogarithmic amplifier ic the output voltage is proportional to the log or to the exponential function antilog of the input signal. The basic output equation of a log amplifier is v vout k ln vinvref. D 8049 c 8049 circuit diagram of antilog circuit log amplifier 8043 diode la8049 la8048 using 8049 bc 303 transistor text. Log amplifier is a linear circuit in which the output voltage will be a constant times the natural logarithm of the input. The voltage across a silicon diode is proportional to the logarithm of the current through it. In fact, a feature of this circuit is the ease with which noninvertingoperation is obtained.
The circuit of an antilog amplifier using op amp is shown in the figure below. But the log of 0, to any base, approaches negative infinity. If v in is the input signal applied to a anti log amplifier then the output is v o k exp a v i where k is proportionality constant, a is constant. But if diode current is too low then the op amp input offsets become then finally choose a max temp difference of the log and antilog diodes. For much higher currents there will be some errors to deal with. The paper presents log and antilog amplifier using current differencing transconductance amplifier cdta. 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. Log and antilog amplifiers explained applications of log. An anti logarithmic amplifier, or an antilog amplifier, is an electronic circuit that produces an output that is proportional to the anti logarithm of the applied input. Logantilog amplifiers to multiply two voltages from single supply.
Logarithmic and antilogarithmic amplifiers electronics. The derivation of the inputoutput equation is similar. An op amp based anti logarithmic amplifier produces a voltage at the output, which is. Note that the transistor is used to turn the input voltage into an input current, with a log function. There are many important nonlinear amplifier circuits, including the log amplifier and the antilog amplifier. An311theory and applications of logarithmic amplifiers.
An opamp based antilogarithmic amplifier produces a voltage at the output, which is. Supplying the input signal to a2 and the reference current to a1 results in a log output that is not inverted from the input. Antilog amplifier circuit, fundamental circuit, drawback of fundamental circuit, equation derivation, analysis, applications. In this video, the log and antilog amplifier circuits using op amp and their applications have been discussed. Log generator circuits are not limited to inverting operation. Logantilog log and antilog amp circuits include the same elements but arranged in different feedback configurations. This section discusses about the opamp based antilogarithmic amplifier in detail. Public circuits, schematics, and circuit simulations on circuitlab tagged antilog. The classic example of this is using a log amp in an automatic gain control loop, to regulate the gain of a variablegain amplifier. Example of a logarithmic amplifier using bipolar transistors instead of diodes. The proposed circuit configuration consists of a single cdta.
Logarithmic amplifier an overview sciencedirect topics. It is well known that some processes such as multiplication and division, can be performed by addition and subtraction of logs. Antilog amplifiers along with log amplifiers are used to perform analogue computations on the input signals. The receiver of a cellular base station, for example, might use the signal from a log amp to regulate the receiver gain. Spice simulation of voltage multiplier using log and antilog amplifier. The circuit of an antilog amplifier using opamp is shown in the figure below. Most logarithmic amplifier ics are available with an external strapping option that makes them operable in either the algorithmic or the exponential antilog mode, as indicator in figure 1. It is noted that by exchanging the positions of the transistor and the resistor, the log. They have numerous applications in electronics, such as.