basic circuit or cad
TRANSCRIPT
Basic Circuit Simulation using OrCAD
Prof. Anish Goel
Capacitors in Series
Series Capacitors add like Parallel Resistors: 1/CT = 1/C1 + 1/Cn
CT = .909uF
2 OrCAD Prof. Anish Goel
Capacitors in Parallel
Parallel Capacitors add like Series Resistors: CT = C1 + Cn
CT = 11uF
3 OrCAD Prof. Anish Goel
Inductors in Series
• Series Inductors add like Series Resistors:• LT = L1 + Ln
• LT = 11uH
4 OrCAD Prof. Anish Goel
Inductors in Parallel
Parallel Inductors add like Parallel Resistors: 1/LT = 1/L1 + 1/Ln
LT = .909uH
5 OrCAD Prof. Anish Goel
Capacitor Review Starts as short circuit, ends as open circuit iC = C*dVC/dt Open circuit at low frequencies Short circuit at high frequencies
6 OrCAD Prof. Anish Goel
Inductor Review Starts as open circuit, ends as short circuit VL = L*dI/dt Short circuit at low frequencies Open circuit at high frequencies
7 OrCAD Prof. Anish Goel
Filters Use frequency response characteristics of C and L to
filter frequency components out of a time domain signal. Low Pass High Pass Band Pass Band Stop
8 OrCAD Prof. Anish Goel
Low Pass Filters RC Low Pass: fcut off frequency = 1/(2πRC)
RL Low Pass: fc = R/(2πL)
• Component selection• RC vs. RL filters
9 OrCAD Prof. Anish Goel
AC Analysis (freq) Logarithmic plot (count by decades) fc defined as –3dB of input, “Half power point” Copy paste data points to excel!
10 OrCAD Prof. Anish Goel
Decibels Measure of gain. Instead of saying gain is 100,000x, some
engineers prefer to say it as 100dB. Power gain: dB = 10 log(Po/Pi) Voltage gain: dB = 20 log(Vo/Vi) Always a relationship
11 OrCAD Prof. Anish Goel
Decibels (cont’d) Useful values: 0dB = 1x 3dB = 2x 6dB = 4x 10dB = 10x 20dB = 100x 30dB = 1000x 3dBm is 3dB above 1mW
12 OrCAD Prof. Anish Goel
Cursor Control Cursor 1: left click left/right arrows
Cursor 2: right click Shift left/right arrows
13 OrCAD Prof. Anish Goel
Cursor, Mark Label
14 OrCAD Prof. Anish Goel
.707? Because we are comparing gains in voltage, not power, we
must use 20log(Vo/Vi). 10^(-3dB/20) = .707V So, Vo = .707Vi at the cut off frequency
15 OrCAD Prof. Anish Goel
Bode Plot (dB, logarithmic)
16 OrCAD Prof. Anish Goel
Common Problems Q: Simulation not making sense A: Make sure you how things are connected.
17 OrCAD Prof. Anish Goel
• RC High Pass: • fc = 1/(2πRC)
• RL High Pass: • fL = R/(2πL)
18 OrCAD Prof. Anish Goel
Band Pass
HP LP
BW = (fc + 3dB) – (fc – 3dB)BW = 200.171kHz – 494.694Hz = 199.676kHz
19 OrCAD Prof. Anish Goel
Response
20 OrCAD Prof. Anish Goel
Band Stop
HP LP
BW = 16.216kHz –6.0833kHz = 10.133kHz
21 OrCAD Prof. Anish Goel
Response
22 OrCAD Prof. Anish Goel
Transformer
Easy to “Step down” or “Step up” an AC voltage (This is why AC is used for home power delivery instead of
DC.) VP/VS = NP/NS => VS = VPNS/NP
Excellent DC filter because VS = NS*dΦ/dt
23 OrCAD Prof. Anish Goel
In PSPICE… Coupling = 1 Lx_Value = Nx
2
should be between 1mH and 1H
24 OrCAD Prof. Anish Goel
Diode
Allow current to flow only in 1 direction Flow from left (annode+) to right (cathode-) is forward
biased. Diode causes a voltage drop due to its activation voltage. Silicon - .7V Germanium - .3V
Cathode connected to a battery is reversed biased. (blocked) Perform DC Sweep and Transient Response (use D1N4002)
25 OrCAD Prof. Anish Goel
Activation Voltage
26 OrCAD Prof. Anish Goel
Transient ResponseHalf Wave Rectifier
27 OrCAD Prof. Anish Goel
Half Wave Rectifier
28 OrCAD Prof. Anish Goel
Full Wave Rectification
29 OrCAD Prof. Anish Goel
Bridge Rectifier
30 OrCAD Prof. Anish Goel
In PSPICE…
31 OrCAD Prof. Anish Goel
Full Wave Rectifier
32 OrCAD Prof. Anish Goel
Smoothing Use capacitor to smooth the ripples of the rectified
wave form.
(Negative voltage)
33 OrCAD Prof. Anish Goel
Regulators
Not in student addition Outputs a clean regulated voltage LM317 and 337 are +/- 2-18V variable regulators LM7805 is 5V regulator Input must be relatively steady or else regulator will fail.
34 OrCAD Prof. Anish Goel