frequency are commonly expressed in dB magnitude vs. Data book curves showing voltage gains vs. Any other required points on the curve can be easily interpolated. In the circuit response world things tend to happen linearly on a log-log frequency scale. I read key values off the graphs, paying particular attention to extreme values, points of inflection, and the frequencies around where the gain drops off. I've chosen to examine the MX3554/BB3554, a 90MHz op amp whose curves are shown in Figure 4.
We can get the values of the op amp's open loop gain, A OL(s), from the data sheet. Note that the open loop gain is a complex number and in general the feedback network can be made up of complex impedances.įigure 3. The circuit in Figure 3 illustrates the problem's setup. Let's take a look at calculating the effects of finite open loop gain on an op amp circuit's response. Of course, not all problems are as simple as the one above but we can apply these simple techniques on a harder problem. You can get a quick feel for the effectiveness of a particular bypass capacitor with this kind of analysis. IMARGUMENT produces an answer in radians so convert to degrees by multiplying by 180 and dividing by π.Īs expected, the impedance of this circuit is very high and capacitive at low frequencies and decreases to a value equal to the resistance at high frequencies. The third and fourth columns use the functions IMABS and IMARGUMENT to convert the complex value in the Z in column into magnitude and phase in degrees. The first parameter is the real part, the second parameter is the imaginary part, and the "j" specifies the standard engineering complex notation where j = √-1. Excel spreadsheet calculates RC impedance. Now, to set this up in Excel we build a spreadsheet with entries for the R, the C, and a frequency sweep as shown in Figure 2.įigure 2. The derivation of the equations for Z in is shown in Figure 1.
The equation for Z in is simply the sum of the impedances of the individual components in series. This is the kind of equivalent circuit you might see for a large value electrolytic bypass capacitor. For example, let's calculate the input impedance of the circuit in Figure 1. The complex function family allows you to work directly with the complex numbers that we need in circuit analysis.
#PUMPS IN SERIES AND PARALLEL PDF TO EXCEL HOW TO#
The first thing you need to know is how to use Excel's COMPLEX function.
0 kommentar(er)
