TRƯỜNG ĐẠI HỌC SƯ PHẠM KỸ THUẬT

TP. HỒ CHÍ MINH

Mô phỏng mạch và hệ thống

MultiSim – Fundamentals

Circuit simulation

Cuong Q. Ngo

1. Introduction

• A simulation in Multisim runs in one of two simulation modes:

– Interactive Simulation Mode

– Analysis Simulation Mode

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1. Introduction

• Interactive Simulation Mode

– This mode is used whenever you click the Run button.

– It performs a time-domain simulation (transient analysis)

until you press the Stop button.

– Data is displayed by the instruments and by the indicator

components.

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1. Introduction

• Analysis Simulation Mode

– This mode is used whenever you press the Simulate

button.

– Allows you to set up a customized analysis and view the

results in the Multisim Grapher during and after the

simulation.

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1. Introduction

• Simulation Methods

– Analogue simulation

– Digital simulation

– Mixed-mode simulation

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1. Introduction

• Analogue simulation

– The goal of analog simulation is to calculate a circuit's

voltages and currents in accordance with Kirchoff's

Current Law(KCL) and Kirchoff's Voltage Law (KVL).

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1. Introduction

• Digital simulation

– To determine the nodal values of a network of elements

which are characterized by a discrete state system.

– Each digital element simply reads the digital signal on its

input, performs some Boolean logic operation, optionally

saves the state, and places a calculated signal on its

output after a specified delay.

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1. Introduction

• Mixed-mode simulation

– Mixed-mode simulation refers to the simulation of circuits

in which analog and digital elements are interconnected.

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1. Introduction

• Analyses

Multisim offers you

many analyses, all of

which use simulation

to generate the data

for the analysis you

want to perform.

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2. DC Operating Point Analysis

• Determines the DC operating point of a circuit.

• The results of DC analysis are usually intermediate values for

further analysis.

• Assumptions:

– AC sources are zeroed out

– Capacitors are open

– Inductors are shorted

– Digital components are treated as a large resistor to

ground.

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DC Operating Point Analysis (cont’d)

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Q1

2SC1815

R1

2.2kΩ

R2

47kΩ

R3

220Ω

R4

10kΩ

VCC

5V

C3

100µF

3. DC Sweep Analysis

• As this analysis is performed in Multisim, the following

procedure is performed:

– The DC operating point is calculated.

– The value from the source is incremented and another DC

operating point is calculated.

• This procedure allows you to simulate the circuit many times,

sweeping the DC values within a pre-determined range.

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3. DC Sweep Analysis (cont’d)

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3. DC Sweep Analysis (cont’d)

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4. AC Analysis

• AC Analysis is used to calculate the frequency response of

linear circuits.

• Applied to an analog circuit, small-signal.

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4. AC Analysis (cont’d)

• Nêu các bước để phân tích đáp ứng tần số cho mạch:

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4. AC Analysis (cont’d)

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4. AC Analysis (cont’d)

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5. Transient Analysis

• Multisim computes the circuit’s response as a function of

time.

• Each input cycle is divided into intervals, and a DC analysis

is performed for each time point in the cycle.

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5. Transient Analysis (cont’d)

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5. Transient Analysis (cont’d)

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R1

1kΩ

C1

1µF

V1

100 Hz 5 V

R1

1kΩ

C1

1µF

V1

1000 Hz 5 V

Integrator circuit ?

Exercise

• Analyze the differentiator circuit

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Filters

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XBP1

IN OUT

Filters (cont’d)

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V1

1.4 Vpk 4kHz 0°

R1

3.9kΩ5% C1

10nF

V2

U1

741

3

2

4

7

6

51

VCC

12V

VEE

-12V

R2

10kΩ

R3

22kΩ

XBP1

IN OUT

Lowpass filter

Filters (cont’d)

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V1

1.4 Vpk 400 Hz 0°

R1

3.9kΩ5%

C1

100nFV2

XBP1

IN OUT

Highpass filter

Filters (cont’d)

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V1

1.4 Vpk 400 Hz 0°

R1

3.9kΩ5%

C1

100nFV2

U1

741

3

2

4

7

6

51

VCC

12V

VEE

-12V

R2

10kΩ

R3

22kΩ

R4

3.9kΩ5% C2

10nF

V2

U2

741

3

2

4

7

6

51

VCC

12V

VEE

-12V

R5

10kΩ

R6

22kΩ

XBP1

IN OUTBandpass filter

MORE ANALYSES

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Parameter Sweep Analysis

• Verify the operation of a circuit by simulation across a range

of values for a component parameter.

• The effect is the same as simulating this circuit several times,

once for each value.

• Three types of analysis that can be performed on the circuit

while the component is manipulated:

– DC Operating Point

– Transient Analysis

– AC Analysis

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Parameter Sweep Analysis (cont’d)

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