Electronic Devices and Amplifier Circuits

Chapter 1 Basic Electronic Concepts and SignalsFrom Figure 1.16 we observe that all poles, denoted as , lie on the left−hand half−plane andthus the system is stable. The location of the zeros, denoted as , is immaterial.b. We use the MATLAB expand(s) symbolic function to express the numerator and denominatorof Gs ( ) in polynomial formsyms s; n=expand((s−1)*(s^2+2*s+5)), d=expand((s+2)*(s^2+6*s+25))n = s^3+s^2+3*s-5d = s^3+s^2+3*s-5and thusGs ( )For this example we are interested in the magnitude only so we will use the scriptnum=3*[1 1 3 −5]; den=[1 8 37 50]; sys=tf(num,den);...w=logspace(0,2,100); bodemag(sys,w); gridThe magnitude plot is shown in Figure 1.17.3s ( 3 + s 2 + 3s – 5)= --------------------------------------------------( s 3 + 8s 2 + 37s + 50)Frequency (rad/sec, log scale)Figure 1.17. Bode plot for Example 1.3Example 1.4It is known that a voltage amplifier has a frequency response of a low−pass filter, a DC gain of80 dB , attenuation of – 20 dB per decade, and the 3 dB cutoff frequency occurs at 10 KHz.Determine the gain (in dB) at the frequencies 1 KHz, 10 KHz , 100KHz , 1 MHz, 10 MHz , and100 MHz .Solution:Using the given data we construct the asymptotic magnitude response shown in Figure 1.18 fromwhich we obtain the data shown on the table below.1−14Electronic Devices and Amplifier Circuits with MATLAB® / Simulink® / SimElectronics® Examples, Third EditionCopyright © Orchard Publicationss