![]() ![]() The frequencies at which each term in the denominator equal 0 are called poles. The frequencies at which each term in the numerator equals 0 are called zeros. The s represents j omega, where omega is equal to 2 times pi times f. H of s represents a transfer function with two poles and two zeros. Now let's take a look at poles and zeroes. Ultimately, we find it's much easier to represent such a large range of values using decibels instead of volts per volt. At 2 megahertz, the open loop gain is 0 dB, which equates to a linear gain of 1 volt per volt. At 1 hertz, the open loop gain is 130 dB, which equates to a linear gain of 3,162,277 volts per volt. While the previous example may not seem like a significant improvement in representing large numbers, let's look at the open loop gain, or AOL, of the OPA188. Similarly, given a gain in decibels, we can convert it to a linear representation using this equation. Substituting 100 volts per volt for the linear gain in the given equation yields 40 dB. For example, let's convert the closed loop gain of an op amp circuit from 100 volts per volt to decibels. This equation shows how to convert from a linear gain in volts per volt to decibels. This slide shows how to convert linear gain values to dB and vice versa. This mechanism is called the decibel, or dB for short. Therefore, it is important to have a mechanism upon which we can represent a large range of values while using small numbers. When working with electronics, we often need to express quantities such as op amp gain, signal-to-noise ratio, common mode rejection ratio, and power supply rejection ratio, whose values have large spans. Why? In order to answer this question, we need to fully understand the concept of bandwidth. When simulated, however, the output voltage is only 154 millivolts peak to peak. The product of the input signal and closed loop gain is 200 millivolts peak to peak. ![]() The input signal, Vn, is 2 millivolts peak to peak. In this transient simulation, the OPA827 is set up in a non-inverting configuration with a closed loop gain of 100 volts per volt. Finally, TINA-TI will be used to correlate simulation results with theoretical calculations. Poles, zeros, Bode plots, cutoff frequency, and the definition of bandwidth will also be discussed. In this video, we'll discuss gain and how it's represented linearly and in decibels. Hello and welcome to the TI Precision Lab discussing op amp bandwidth, Part 1. ![]()
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