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Build an Op Amp SPICE Model from Its Datasheet – Part 2
Sunday, November 14th, 2010Summary:
Part 1 of this article shows how to create a behavioral model of an operational amplifier based on the following parameters found in the datasheet: Input and output resistance, input capacitance, DC gain, and offset voltage. As an example I chose Analog Devices’ ADA4004. Let’s continue building this model to simulate the Gain Bandwidth Product.
Build an Op Amp SPICE Model from Its Datasheet – Part 1
Monday, October 11th, 2010Summary:
Why do you need to build your own Op Amp model? Most Op Amp manufacturers have SPICE models for their components and make them available for free. Then why should you know how to build one? Well, not everything has a model and that is why, sometimes, you have to build your own. Also, it may be necessary to study a circuit to see what happens if you change the Op Amp slew rate or bandwidth, offset, and so on. Sometimes the manufacturer own model does not work, as a user found out and posted a question in this forum. I told him that the model does not work and advised him to build his own. …
Using the Summing Amplifier as an Average Amplifier
Sunday, July 4th, 2010Summary:
The summing amplifier can output the average of two, three or more signals. This is different than a signal average. The summing amplifier cannot, for example, output the average of a triangle signal. For that, you need an integrator to perform the average in the analog realm, or you need to sample the signal and calculate the average with a microcontroller. This type of average is the signal average in the time domain. I will write an article about the average of a signal in a near future.
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.
Design a Bipolar to Unipolar Converter with a 3-input Summing Amplifier
Sunday, January 31st, 2010Summary:
Since the publication of Design a Bipolar to Unipolar Converter to Drive an ADC, several readers contacted me with requests to help in solving their particular converter. The common problem they had was the fact that the components’ calculation resulted in a negative value for at least one resistor.
To provide a solution, first we need to understand the root cause of the problem. Let’s take one of the circuits I received and analyze it.
The reader wrote that he would like to drive an ADC with the input range of 0 to 2.5V from a signal with the range of –5V to +5V, connected at V1.
How to Design a Summing Amplifier Calculator
Monday, January 11th, 2010Summary:
In this article, you can download a Summing Amplifier Calculator in the form of a spreadsheet. You can input the voltage range, output range, a reference voltage and a choice of two resistors. The calculator gives you the answer for the remaining resistors. Also, this article explains the mathematical steps towards building the calculator.
Bipolar to Unipolar Converters Based on a Summing Amplifier Configuration
Monday, December 28th, 2009Summary:
In a previous article I presented a method for designing a bipolar to unipolar converter using a summing amplifier. In this article I am going to show more examples of bipolar to unipolar converters which are based on a summing amplifier configuration. You can adapt them to your needs if you use the method I described in the previous article.
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