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Measure a Bipolar Signal with an Arduino Board
Sunday, August 14th, 2011Summary:
Arduino is a popular family of open source microcontroller boards. Hobbyists, students and engineers all over the world use this platform to quickly design and prototype a microcontroller driven circuit. One of its interfaces with the analog world is the ADC. Since these boards are mostly designed around an ATMEL ATmega32 or ATmega168 microcontroller, the ADC has 8 inputs and 10-bit resolution, making it suitable for many applications.
Apply Thevenin’s Theorem to Solve a Negative Resistance Circuit, or Current Source
Monday, February 14th, 2011Summary:
The circuit in Figure 1 is a good example of applying Thevenin’s Theorem to solve a circuit with dependent supplies. It is a negative resistance circuit and it was posted in this forum with a call for solution verification for IL as a function of Vin. Since this fits very well with my plans to write more about Thevenin’s Theorem, I decided to post the solution here.
Build an Op Amp SPICE Model from Its Datasheet – Part 3
Friday, December 31st, 2010Summary:
In Part 2, we left off at the open-loop bode plot. We saw that it resembles the datasheet. However, our op amp example, ADA4004 from Analog Devices, shows an extra pole after 1 MHz. Indeed, the phase starts dropping after 1 MHz and becomes 45 degrees at 17 MHz. Therefore, we need another pole in our model at 17 MHz.
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.
An Op Amp Gain Bandwidth Product
Monday, October 18th, 2010Summary:
I can see some chat on internet about the operational amplifier gain bandwidth product. People are interested in having a better understanding of this parameter, as it appears in any op amp datasheet and it is used in many articles and books. In this article I will describe this parameter and show you an example with Analog devices’ ADA4004, which is a precision amplifier.
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. …
An Ideal Operational Amplifier Simulation Model
Saturday, August 28th, 2010Summary:
You worked hard on your schematic, you calculated everything, you feel confident that it will work. To be sure though, before committing the schematic to copper, you want to simulate it. You develop a SPICE simulation schematic and, surprise, things don’t work. What’s going on?
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