# LOG AND ANTILOG AMPLIFIER PDF

Antilog amplifiers along with log amplifiers are used to perform analogue computations on the input signals. The circuit of an antilog amplifier. 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. EXPERIMENT 8: Log and Antilog Amplifiers. Objectives: To understand the behavior of logarithmic and antilogarithmic amplifiers. Materials and Equipment.

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This section discusses about the op-amp based anti-logarithmic amplifier in detail. Very similar question from a month ago: The system bandwidth is narrower for small signals because emitter resistance increases for small currents.

## Log and AntiLog Amplifiers

Such circuit techniques are used in integrated log amps: Logarithmic amplifier gives the output proportional to the logarithm of input signal. Antilog amps are used together with log amps to wmplifier analog computation. Using the concept of virtual short between the input terminals of an opamp the voltage at inverting terminal will be zero volts.

Please think about what you are doing antilo your simulation. This section discusses about the op-amp based logarithmic amplifier in detail. The analysis is the same as above for the transdiode connection, but the logarithmic range is limited to four or five decades because the base current adds to the collector current.

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. Then verify your design specs with sweeping voltages on the inputs and compute the gain and offset errors vs input.

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Does this seem reasonable? Anti log amplifier is one which provides output proportional to the anti log i. An anti-logarithmic amplifieror an anti-log amplifieris an electronic circuit that produces an output that is ampplifier to the anti-logarithm of the applied input. So this is another tradeoff for diode size vs bandwidth vs temp rise. The diode dynamic resistance also drops with rising log current until saturated where the bulk resistance limits the minimum resistance.

Figure next slide shows the use of a second, matched, transistor for offset compensation and a temperature-dependent gain for gain compensation.

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.

### Linear Integrated Circuits Applications Log And Anti Log Amplifiers

The current inverter in Figure below amplifoer two matched n-p-n transistors and a precision op amp to achieve accurate current inversion. Using a p-n-p transistor changes the polarity of input signals acceptable but limits the logarithmic range because of the degraded performance of p-n-p transistors compared to n-p-n transistors www. It means zero volts is applied to its non-inverting input terminal. IC log amps may cost about ten abd the components needed to build a discrete-component log amp.

So, the voltage ampligier the inverting input terminal will be zero volts. Matched temperature by thermal coupling is desired or minimize self heating for low T rise. Your email address will not be published. I know there is problem with the last stage, the last opamp should give me gain: This is the basic layout of the circuit: I’m trying to build an analog multiplier that takes any two voltages and produces the product for them This is the basic layout of the circuit: It is well ammplifier that some processes such as multiplication and division, can be performed by addition and subtraction of logs.

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They have numerous applications in electronics, such as: Since the non inverting terminal of opamp is at ground potential. The final output is developed by an inverting amplifier with a voltage gain of —K2. You’ve simulated it, so why do you ask if it works for you? To get the logarithm of a signal voltage use a Log amplifier.

In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground.

The logarithmic circuit can be redrawn as follows. Tony EE rocketscientist 62k 2 21 But this depends on your thermal design. Then a properly working multiplier should give you 20 volts out. One usually starts with a spec for Input and Output voltage range and max error vs input.

So, the voltage at its inverting input terminal will be zero volts. Some integrated log amps have uncommitted elements allowing us to implement antilog amps. But if diode current is too low then the OP Amp input offsets become significant compared the the log1, log2 outputs.

You have 4 volts and 5 volts as your antilov.

These basic circuits needs additional components to improove the overall performance, i.