0195136047.pdf

172 TIME-DEPENDENT CIRCUIT ANALYSIS

requests frequency analysis with 20 points per decade, which is usually a suitable value, starting at

10 Hz and ending at 1 MHz. Note that the frequencies would be uniformly spaced on a logarithmic

frequency scale.

EXAMPLE E3.5.3

Develop a PSpice program and use PROBE to obtain Bode plots of the magnitude and phase of

the transfer functionV ̄out/V ̄infor the high-pass filter circuit shown in Figure E3.5.3(a) along with

node numbers. This filter is to pass components above 1 kHz and reject components below 1 kHz.

−

+

−

+

Vin = 1 ∠ 0 ° Vout

(a)

R = 314.1 Ω

L = 50 mH

1 2 C^ = 0.507 μF 3

0

Figure E3.5.3(a) High-pass

filter circuit. (b) Magnitude

Bode plot.(c)Phase plot.

|H(f)|

dB

(b)

100 Hz

− 60

− 80

− 40

− 20

0

20

10 Hz 1.0 kHz 10 kHz 100 kHz

(c)

100 Hz

180 °

0 °

45 °

90 °

135 °

10 Hz 1.0 kHz 10 kHz 100 kHz

Solution

The transfer functionH(f) ̄ =V ̄out/V ̄inis numerically equal to V(3) since the amplitude ofV ̄in

is given as 1 V. Thus to obtain a plot of the transfer-function magnitude in decibels, the PROBE

menu commands can be used to request a plot of VDB (3). A Bode plot of the transfer function

can be obtained by requesting a plot of VP (3). The program is as follows:

EXAMPLE E3.5.3

THE CIRCUIT DIAGRAM IS SHOWN IN FIGURE E3.5.3(a)

VIN10AC1

R 1 2 314.1

C 2 3 0.507 UF

L3050MH