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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Then verify your design specs with sweeping voltages on the inputs and compute the lkg and offset errors vs input. By summing the outputs of two log amplifiers, you get the logarithm of the product of the two original input voltages. SPICE simulation of voltage multiplier using log and antilog amplifier. But this depends on your thermal design.
It is well known that some processes such as multiplication and ane, can be performed by addition and subtraction of logs. This chapter discusses about the Logarithmic amplifier and Anti-Logarithmic amplifier in detail. Documents Flashcards Grammar checker.
In the circuit shown above, the non-inverting input terminal of the op-amp is connected to ground.
Hence applying KCL at inverting amplidier of opamp, we get. Amplkfier Classification of internet video content. So, the voltage at the inverting input terminal will be zero volts. Very similar question from a month ago: This section discusses about the op-amp based anti-logarithmic amplifier in detail. Constant terms lpg omitted for simplicity.
These basic circuits needs additional components to improove the overall performance, i. Sign up using Facebook. 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. To investigate its stability, refer to the incremental model, where the BJT has been replaced by its common-base smallsignal model.
In the anttilog circuit, the non-inverting input terminal of the op-amp is connected to ground. Gain of logarithmic amplifier. Temperature compensation can be achieved by the same technique shown for log amps. That means zero volts is applied at the non-inverting input terminal of the antilov. It is called four-quadrant since inputs and output can be positive or negative. One usually starts with a spec for Input and Output voltage range and max error vs input.
So this is another tradeoff for diode size vs bandwidth vs temp rise. Negative voltages or currents can be first rectified and then applied to the log amp, but this adds the errors from the rectifier.
The system bandwidth is narrower for small signals because emitter resistance increases for small currents.
Log and AntiLog Amplifiers
Sign up using Email and Password. Tony EE rocketscientist 62k 2 21 I know there is problem with the last stage, the last opamp should give me gain: Temperature compensation must correct both error sources.
The two output voltages from the log amplifiers are added and inverted by the unity-gain summing amplifier to produce the following result: Anti log amplifier is one which provides output proportional to the anti log i. Logarithmic amplifier operation The circuit diagram of logarithmic amplifier is as shown below logarithmic amplifier. IC log amps may cost about ten times the components needed to build a discrete-component log amp.
Unclear what you’re asking. Since the non inverting terminal of opamp is at ground potential.
The K values control the R value which controls the diode current which can lead to errors if there is self heating which is the NTC Shockley Effect. The amplivier log amplifier can be redrawn as follows. 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.
logarthmic, anti logarthmic amplifiers | ECE Tutorials
Then a properly working multiplier should give you 20 volts out. The circuit diagram of logarithmic amplifier is as shown below.
You’ve simulated it, so why do you ask if it works for you? I’m trying to amplicier an analog multiplier that takes any two voltages and produces the product for them. Omitting R1 yields a currentinput log amp. Home Questions Tags Users Unanswered.
Gain of Anti log amplifier. Then, by taking the antilogarithm, you get the product of the two input voltages as indicated in the following equations: