CIRCUIT ANALYSIS USING NGSPICE TECHNICAL WORKSHOP MARATHON 2012 CIRCUIT ANALYSIS USING NGSPICE VISHNU V 2nd Year M.Tech VLSI and Embedded Systems Govt. Model Engineering College, Thrikkakara

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 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. 3

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 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 3.3nF R n1 0 1k

Writing NETLIST Control Lines .CONTROL TRAN 0.01ms 10ms PLOT V(n0) V(n1) END Lines .ENDC .END

Total NETLIST A Simple RC High pass filter V1 n0 0 SIN(0 10 1kHz) C1 n0 n1 3.3nF R n1 0 1k .CONTROL TRAN 0 0.01ms 10ms PLOT V( n0) V(n1) .ENDC .END

SIMULATION STEPS Save the above file as rc_filter.cir Terminal Save the above file as rc_filter.cir STEP 1 : Open Terminal and type ngspice Open Terminal and Type ngspice Ngspice command terminal opens

SIMULATION STEPS 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 BASH TERMINAL WAVE FORM WINDOW TRANSIENT ANALYSIS OUTPUT BASH TERMINAL WAVE FORM WINDOW

ANALYSIS OF WAVEFORM Analyse the waveform I N P U T OUTPUT

NETLIST CREATION USING PART II NETLIST CREATION USING gEDA SCHEMATIC EDITOR

STEPS 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

DRAWING CIRCUIT IN gEDA SCHEMATIC EDITOR SAVE THE ABOVE SCHEMATIC AS rc_filter.sch

CONVERING SCHEMATIC TO NETLIST Output File name Schematic Name gnetlist -g spice -o rc_filter.net rc_filter.sch

NETLIST OBTAINED FROM SCHEMATIC rc_filter.net

SIMULATING THE NETLIST

SIMULATING THE NETLIST Name of the NETLIST created using gnetlister

SIMULATING THE NETLIST

SIMULATING THE NETLIST : TRANSIENT ANALYSIS Final Value Indicates Transient Analysis Increment value

SIMULATING THE NETLIST : TRANSIENT ANALYSIS

SIMULATING THE NETLIST : TRANSIENT ANALYSIS PLOT V(2) V(1)

ANALYSIS OF THE WAVEFORM GREEN COLOUR : INPUT WAVE RED COLOUR : OUTPUT WAVEFORM

WHY THE AMPLITUDE OF THE OUTPUT WAVEFORM IS VERY LESS ??

Cut off frequency of the high pass filter is given by, REASONS 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

A Simple RC High pass filter V1 n0 0 SIN(0 10 500kHz) C1 n0 n1 3.3nF MODIFIED NETLIST A Simple RC High pass filter V1 n0 0 SIN(0 10 500kHz) C1 n0 n1 3.3nF R n1 0 1k .CONTROL TRAN 0.0001ms 0.1ms PLOT n0 n1 .ENDC .END 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 filter V1 n0 0 SIN(0 10 500kHz) C1 n0 n1 3.3nF R n1 0 1k .CONTROL AC LIN 1000 0.1Hz 1000kHz PLOT V(n1) .ENDC .END AC ANALYSIS

AC ANALYSIS PLOT I

NETLIST FOR AC ANALYSIS OF HIGH PASS FILTER A Simple RC High pass filter V1 n0 0 SIN(0 10 500kHz) C1 n0 n1 3.3nF R n1 0 1k .CONTROL AC DEC 10 100Hz 10000kHz PLOT 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

HIGH PASS FILTER AS DIFFERENTIATOR 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

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

CLIPPER CIRCUITS DOUBLE CLIPPER CLIPPING LEVELS : +5V and -5V WRITE NETLIST AND OBTAIN THE OUTPUT WAVEFORM

DOUBLE CLIPPER OUTPUT WAVEFORM

CLAMPER CIRCUITS SIMPLE POSITIVE CLAMPER CIRCUIT

OUTPUT WAVEFORM

LAB SESSION EXPERIMENTS RC HIGH PASS CIRCUIT AND DIFFERENTIATOR RC LOW PASS CIRCUIT AND INTEGRATOR RECTIFIER CIRCUITS CLIPPER CIRCUITS CLAMPER CIRCUITS

PLOT THE FOLLOWING WAVEFORM USING NGSPICE ASSIGNMENT I PLOT THE FOLLOWING WAVEFORM USING NGSPICE

52