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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.
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.
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.
Differential Amplifier Calculator
Sunday, February 7th, 2010Summary:
If you need to design a differential amplifier, here is a handy calculator. All you need to define are the input range, the output range and a choice of a voltage reference. The default values for this calculator are set for a unipolar to bipolar converter.
The Non-Inverting Amplifier Output Resistance
Wednesday, December 23rd, 2009Summary:
It is customary to consider the output resistance of the non-inverting amplifier as being zero, but why is that? An Op Amp’s own output resistance is in the range of tens of ohms. Still, when we connect the Op Amp in a feedback configuration, the output resistance decreases dramatically. Why?
How to Derive the Inverting Amplifier Transfer Function
Thursday, November 26th, 2009Summary:
Widely used in Analog Design, the inverting amplifier in Figure 1 has a simple transfer function. What is the proof of this function?
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.
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