Basic circuit or cad

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


Inductors in Series

• Series Inductors add like Series Resistors:• LT = L1 + Ln

• LT = 11uH


Inductors in Parallel

Parallel Inductors add like Parallel Resistors: 1/LT = 1/L1 + 1/Ln

LT = .909uH


Capacitor Review Starts as short circuit, ends as open circuit iC = C*dVC/dt Open circuit at low frequencies Short circuit at high frequencies


Inductor Review Starts as open circuit, ends as short circuit VL = L*dI/dt Short circuit at low frequencies Open circuit at high frequencies


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


Low Pass Filters RC Low Pass: fcut off frequency = 1/(2πRC)

RL Low Pass: fc = R/(2πL)

• Component selection• RC vs. RL filters


AC Analysis (freq) Logarithmic plot (count by decades) fc defined as –3dB of input, “Half power point” Copy paste data points to excel!


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


Decibels (cont’d) Useful values: 0dB = 1x 3dB = 2x 6dB = 4x 10dB = 10x 20dB = 100x 30dB = 1000x 3dBm is 3dB above 1mW


Cursor Control Cursor 1: left click left/right arrows

Cursor 2: right click Shift left/right arrows


Cursor, Mark Label


.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


Bode Plot (dB, logarithmic)


Common Problems Q: Simulation not making sense A: Make sure you how things are connected.


• RC High Pass: • fc = 1/(2πRC)

• RL High Pass: • fL = R/(2πL)


Band Pass

HP LP

BW = (fc + 3dB) – (fc – 3dB)BW = 200.171kHz – 494.694Hz = 199.676kHz


Response


Band Stop

HP LP

BW = 16.216kHz –6.0833kHz = 10.133kHz


Response


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


In PSPICE… Coupling = 1 Lx_Value = Nx

2

should be between 1mH and 1H


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)


Activation Voltage


Transient ResponseHalf Wave Rectifier


Half Wave Rectifier


Full Wave Rectification


Bridge Rectifier


In PSPICE…


Full Wave Rectifier


Smoothing Use capacitor to smooth the ripples of the rectified

wave form.

(Negative voltage)


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.


Basic circuit or cad

Education

Transcript of Basic circuit or cad