CIRCUIT ANALYSIS USING NGSPICE VISHNU V 2 nd Year M.Tech VLSI and Embedded Systems Govt. Model...
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Transcript of CIRCUIT ANALYSIS USING NGSPICE VISHNU V 2 nd Year M.Tech VLSI and Embedded Systems Govt. Model...
CIRCUIT ANALYSIS USING NGSPICE
VISHNU V
2nd Year M.Tech VLSI and Embedded Systems
Govt. Model Engineering College, Thrikkakara
TECHNICAL WORKSHOP MARATHON 2012
CONTENTS SIMULATING A CIRCUIT IN NGSPICE
EXAMPLE CIRCUIT
NETLIST CREATION USING gEDA SCHEMATIC EDITOR ANALYSIS OF BASIC CIRCUITS
HIGH PASS CIRCUIT AND DIFFERENTIATOR
LOW PASS CIRCUIT AND INTEGRATOR
RECTIFIER CIRCUITS
CLIPPER CIRCUITS
CLAMPER CIRCUITS
Simulating a Circuit using NGSPICE
3
Steps
Mark the nodes present in the circuit using numbers or symbols (Try to mark Ground node by '0')
Write the netlist (use texteditors such as gedit or vi editor etc)for the circuit satisfying all the rules and regulations.
Save the netlist using .cir or .net extension.
Simulating a Circuit using NGSPICE
Open ngspice command window by typing ngspice in terminal(bash,sash etc)
Give the name of the saved netlist in ngspice command window.
EXAMPLE CIRCUIT
Simulation of a simple RC filter using NGSPICE
EXAMPLE CIRCUIT
Here there are three nodes
n0 n1 0
Also the components present are
A sinusoidal voltage source A 3.3nF capacitor A 1k resistor
Writing NETLIST
Title Line (First Line )
A simple RC High pass filter
Component connections
V1 n0 0 SIN(0 10 1kHz)C1 n0 n1 3.3nFR n1 0 1k
Writing NETLIST
Control Lines
.CONTROLTRAN 0.01ms 10msPLOT V(n0) V(n1)
END Lines
.ENDC
.END
A Simple RC High pass filterV1 n0 0 SIN(0 10 1kHz)C1 n0 n1 3.3nFR n1 0 1k.CONTROLTRAN 0 0.01ms 10msPLOT V( n0) V(n1).ENDC.END
Total NETLIST
SIMULATION STEPS
Open Terminal and Type ngspice
Save the above file as rc_filter.cir STEP 1 : Open Terminal and type ngspice
Ngspice command terminal opens
Terminal
STEP 2 : Give the file name of the netlist we have written ie rc_filter.cir
Give the file name of the netlist and press enter
SIMULATION STEPS
TRANSIENT ANALYSIS OUTPUT
WAVE FORM WINDOWBASH TERMINAL
SIMULATION STEPS
Analyse the waveform
INPUT
ANALYSIS OF WAVEFORM
OUTPUT
PART II
NETLIST CREATION USING gEDA SCHEMATIC EDITOR
Draw the schematic of the circuit using gEDA schematic editor
Save the file with extension .sch
Convert .sch file to .net file using gnetlister. Command :gnetlist -g spice -o rc_filter.net rc_filter.sch
STEPS
SAVE THE ABOVE SCHEMATIC AS rc_filter.sch
DRAWING CIRCUIT IN gEDA SCHEMATIC EDITOR
gnetlist -g spice -o rc_filter.net rc_filter.sch
Output File name Schematic Name
CONVERING SCHEMATIC TO NETLIST
rc_filter.net
NETLIST OBTAINED FROM SCHEMATIC
SIMULATING THE NETLIST
Name of the NETLIST created using gnetlister
SIMULATING THE NETLIST
SIMULATING THE NETLIST
Indicates Transient AnalysisIncrement value
Final Value
SIMULATING THE NETLIST : TRANSIENT ANALYSIS
SIMULATING THE NETLIST : TRANSIENT ANALYSIS
PLOT V(2) V(1)
SIMULATING THE NETLIST : TRANSIENT ANALYSIS
GREEN COLOUR : INPUT WAVERED COLOUR : OUTPUT WAVEFORM
ANALYSIS OF THE WAVEFORM
WHY THE AMPLITUDE OF THE OUTPUT WAVEFORM IS VERY LESS ??
The Circuit is a High pass filter, so it passes only high frequency signals.
We have given an input sinusoidal waveform of Amplitude = 10V and Frequency = 1kHz
Cut off frequency of the high pass filter is given by, cutoff frequency= 1/(2*pi*R*C) Here in this case Cutoff frequency (3 dB frequency ) = 48.22kHZ So, Give input sine wave frequency >= 48.22 kHz
REASONS
A Simple RC High pass filterV1 n0 0 SIN(0 10 500kHz)C1 n0 n1 3.3nFR n1 0 1k.CONTROLTRAN 0.0001ms 0.1msPLOT n0 n1.ENDC.END
MODIFIED NETLIST
NEW INPUT FREQUENCY
OUTPUT WAVEFORM
AC ANALYSIS OF HIGH PASS FILTER
FOR AC ANALYSIS THE CONTROL SIGNAL IS
.AC <sweep type> <points value> <start frequency> <end frequency>
(sweep type is either LIN,OCT or DEC)
Examples
.AC LIN 16 60 600KHz .AC DEC 20 1 10kHz
NETLIST FOR AC ANALYSIS OF HIGH PASS FILTER
A Simple RC High pass filterV1 n0 0 SIN(0 10 500kHz)C1 n0 n1 3.3nFR n1 0 1k.CONTROLAC LIN 1000 0.1Hz 1000kHzPLOT V(n1).ENDC.END
AC ANALYSIS
AC ANALYSIS PLOT I
NETLIST FOR AC ANALYSIS OF HIGH PASS FILTER
A Simple RC High pass filterV1 n0 0 SIN(0 10 500kHz)C1 n0 n1 3.3nFR n1 0 1k.CONTROLAC DEC 10 100Hz 10000kHzPLOT DB(V(n1)/V(n0)).ENDC.END
AC ANALYSIS
AC ANALYSIS PLOT II
HOW A HIGH PASS FILTER CAN BE CONVERTED TO A DIFFERENTIATOR CIRCUIT
The Condition in which a high pass filter acts as a differentiator circuit is given by
RC << 0.0016T ; Where T = Time period of the input signal
Question ?
Design a Differentiator Circuit which takes a pulse waveform of frequency 1 kHz and perform its transient analysis using NGSPICE....
Take the capacitor value as C = 3.3nF
HIGH PASS FILTER AS DIFFERENTIATOR
DIFFERENTIATOR TRANSIENT RESPONSE
With RESISTOR VALUE, R = 47k
DIFFERENTIATOR TRANSIENT RESPONSE
With RESISTOR VALUE, R = 10k
RC LOW PASS FILTER
RC LOWPASS FILTER AC ANALYSIS PLOT
RC LOWPASS FILTER AS INTEGRATOR
RECTIFIER CIRCUIT
WRITE THE NETLIST AND PLOT THE WAVEFORMS
RECTIFIER CIRCUIT OUTPUT
CLIPPER CIRCUITS
POSITIVE CLIPPER
CLIPPING LEVEL : +5V
WRITE NETLIST AND OBTAIN THE OUTPUT WAVEFORM
POSITIVE CLIPPER OUTPUT WAVEFORM
+5V
CLIPPER CIRCUITS
DOUBLE CLIPPER
CLIPPING LEVELS : +5V and -5V
WRITE NETLIST AND OBTAIN THE OUTPUT WAVEFORM
DOUBLE CLIPPER OUTPUT WAVEFORM
+5V
r
-5V
CLAMPER CIRCUITS
SIMPLE POSITIVE CLAMPER CIRCUIT
OUTPUT WAVEFORM
LAB SESSION
EXPERIMENTS
1. RC HIGH PASS CIRCUIT AND DIFFERENTIATOR
2. RC LOW PASS CIRCUIT AND INTEGRATOR
3. RECTIFIER CIRCUITS
4. CLIPPER CIRCUITS
5. CLAMPER CIRCUITS
ASSIGNMENT I
PLOT THE FOLLOWING WAVEFORM USING NGSPICE
52