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A Summing and Differential Amplifier with One Op Amp
Sunday, April 18th, 2010Summary:
In a comment, one of my readers asked me what is the transfer function of the non-inverting summing amplifier in Figure 1, when R3 is connected to a reference voltage instead of ground. Well, this is a summing amplifier with a differential configuration.
How to Derive the Instrumentation Amplifier Transfer Function
Sunday, August 30th, 2009Summary:
The Instrumentation Amplifier (IA) resembles the differential amplifier, with the main difference that the inputs are buffered by two Op Amps. Besides that, it is designed for low DC offset, low offset drift with temperature, low input bias currents and high common-mode rejection ratio. These qualities make the IA very useful in analog circuit design, in precision applications and in sensor signal processing.
How to Derive the Transfer Function of the Inverting Summing Amplifier
Monday, August 17th, 2009Summary:
The inverting summing amplifier does exactly what its name says: adds the input signals and inverts the result. This amplifier presents a major advantage versus the non-inverting summing amplifier. The input signals are added with their own gain. The disadvantage is the inversion of the sum, which might not be desirable in some cases. How can we derive this function? What is the transfer function of the inverting summing amplifier with 3, 4, or n inputs? This article answers all these questions.
The Transfer Function of the Non-Inverting Summing Amplifier with “N” Input Signals
Sunday, August 9th, 2009Summary:
In a previous article, How to Derive the Summing Amplifier Transfer Function, I deduced the formula for the non-inverting summing amplifier with two signals in its input. But what if we have 3, 4 or an n number of signals? Can we add them all with one amplifier?
How to Derive the Summing Amplifier Transfer Function
Thursday, July 9th, 2009Summary:
The summing amplifier, or the non-inverting summing amplifier, is an analog processing circuit with the transfer function (the summing amplifier formula as some say) shown in the following equation. (1) The first term of the product is the actual summing, while the second term is a gain due to the R3 and R4 resistors. I [...]
Converting a Differential Amplifier into a Summing Amplifier
Thursday, June 25th, 2009Summary:
Is there any link between a differential amplifier and a summing amplifier? Yes, it is. They can be easily converted one into the other one. While this article shows the conversion, the main purpose is to demonstrate how the same circuit can be viewed as a differential amplifier or as a summing amplifier, depending on the voltage levels in its inputs.
The Differential Amplifier Common-Mode Error – Part 1
Wednesday, May 20th, 2009Summary:
The common-mode voltage can bring errors in the differential amplifier applications. What is the common-mode voltage? The common-mode voltage is the voltage level common to both inverting and non-inverting inputs of the differential amplifier. In many applications, the differential amplifier is used to amplify the difference between two voltages, for later processing, or to isolate a signal from common-mode noise, or to amplify a signal that rides on top of some large voltage level. If the common-mode voltage is not rejected, it appears as an error at the amplifier output.
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