Java程序辅导

6.101 Spring 2020 Lecture 4
Introduction to LTspice
Acknowledgment:  LTspice material based in part by 
Devon Rosner (6.101 TA 2014), Engineer, Linear Technology
SPICE
• Simulation Program with Integrated 
Circuit Emphasis
• Developed in 1973 by Laurence Nagel at 
UC Berkeley’s Electronics Research 
Laboratory 
• Dependent on user defined device 
models
6.101 Spring 2020 Lecture 4 2
Netlists
6.101 Spring 2020 Lecture 4
Components
Commands
3
LTspice
• Developed in 1998 by Mike Engelhardt at Linear 
Technology Corporation
• GUI, simulator, and schematic -> netlist for SPICE 
• FREE and comes with tons of models
6.101 Spring 2020 Lecture 4
You do this Ltspice makes this
4
Getting Started
6.101 Spring 2020 Lecture 4
THAT’S IT!
These buttons are where you will live
5
Component to Menu Item Matchup
6.101 Spring 2020 Lecture 4 6
Net Labels
6.101 Spring 2020 Lecture 4
By labeling nets you can avoid a giant mess of wires. Always use 
these for at least your power supplies. When you start making 
large circuits, your power supplies will provide energy all over your 
schematic.
7
Adding Other Components
6.101 Spring 2020 Lecture 4
Devices besides basic resistors, capacitors, and 
inductors are found from this button
8
Op-Amps
6.101 Spring 2020 Lecture 4
There are no “ideal” op-amps in reality. BUT, there are in LTspice.
PAY CLOSE
ATTENTION
TO THE TEXT
You must 
literally include
.lib opamp.sub
in your netlist
or schematic
as a SPICE 
directive.
9
Op-Amps
Though listed as “ideal” there are still 2 parameters
you can tweak.
6.101 Spring 2020 Lecture 4 10
Open Loop Gain: As this 
number approaches infinity, 
the Op Amp becomes more 
“ideal”. Look at some Op Amp
data sheets to see some real 
open loop gains.
Gain Bandwidth: As this 
number approaches infinity, 
the Op Amp becomes more 
“ideal”. To check if this is high
enough, multiply your desired 
Closed Loop Gain by your 
highest desired output 
frequency. 
Op-Amps
To more accurately model a real Op Amp not available in LTspice, 
UniversalOpamp2 has many tweakable parameters.
6.101 Spring 2020 Lecture 4 11
Open loop gain, gain 
bandwidth, slew rate, current 
limit, rail-rail voltage, input 
voltage offset, phase margin, 
Rin, etc.
Editing Components
6.101 Spring 2020 Lecture 4
Just right click the
component
12
Editing Components
6.101 Spring 2020 Lecture 4
This is the basic voltage source menu.
Use this for DC sources such as power
supplies or bias voltages.
But what 
about this?
13
Editing Components
6.101 Spring 2020 Lecture 4
Voltage sources can produce many test signals.
PWL can be used to construct any signal.
14
Selecting Device Model
6.101 Spring 2020 Lecture 4
There are no “ideal” BJT’s, MOSFET’s, etc. You can select a model 
(provided by LTspice), download models, or create your own.
15
Simulation: Transient
Transient simulation gives Voltage and/or Current 
vs.time.
6.101 Spring 2020 Lecture 4
These are transient 
parameters for 
a voltage source
16
Simulation: Transient
6.101 Spring 2020 Lecture 4
This is all you
really need
17
Random Tangent: Parameters
6.101 Spring 2020 Lecture 4
This is a 
parameter
You MUST define all of your parameters. 
The “list” command allows you to choose 
multiple values (simulation simulates each 
value separately).
18
What Should My Circuit Do?
• The very first step to any simulation is to know how 
your circuit should behave. Simulation is a verification 
tool NOT A CIRCUIT SOLVER.
• So how should this circuit behave?
6.101 Spring 2020 Lecture 4 19
Here’s Where You Write the Solution
6.101 Spring 2020 Lecture 4 20
Here’s Where You Write the Solution
6.101 Spring 2020 Lecture 4
vx
vo
i1
i2
i3
A DOUBLE POLE!!
21
Expected Behavior
• Double pole is at:
• We expect frequencies up to this point to be 
large, but frequencies above to quickly drop 
off due to the -40 dB/decade characteristic 
of the double pole
6.101 Spring 2020 Lecture 4 22
Transient Simulation
6.101 Spring 2020 Lecture 4
Hover over the desired 
voltage node to be probed and 
click when you see this symbol
**This is the current probe
23
Transient Simulation
6.101 Spring 2020 Lecture 4
1 kHz
10 kHz
100 kHz
1 MHz
24
AC Simulation
6.101 Spring 2020 Lecture 4
This is the AC
parameter.
Just set the
amplitude to 1
AC simulation gives Voltage and/or Current 
vs.frequency.
25
AC Simulation
6.101 Spring 2020 Lecture 4 26
Extra Fun: Math in LTspice
6.101 Spring 2020 Lecture 4
Remember:
27
Transient Simulation
6.101 Spring 2020 Lecture 4
It’s the same as before!
28
Even More Fun
6.101 Spring 2020 Lecture 4 29
*Note: You can try out some math functions in the simulator 
window, too! (ex: V(Vo)/V(Vi)). 
AC Simulation
6.101 Spring 2020 Lecture 4 30
Temperature as a Variable
• PTAT current source
6.101 Spring 2020 Lecture 4 31
Temperature as a Variable
6.101 Spring 2020 Lecture 4 32
Including External Models
6.101 Spring 2020 Lecture 4 33
• PFET model
• Includes 
parameters to 
describe MOS 
device physics
Making Things Pretty
6.101 Spring 2020 Lecture 4 34
Making Things Pretty
6.101 Spring 2020 Lecture 4 35
Making Things Pretty
Bob Reay of Linear Technology has provided a nifty tool on his website to 
give LTspice circuits an even better makeover: 
http://reaylabs.com/tools/SchematicViewer/SchematicViewer.html
6.101 Spring 2020 Lecture 4 36
Before:
Making Things Pretty
Bob Reay of Linear Technology has provided a nifty tool on his website to 
give LTspice circuits an even better makeover: 
http://reaylabs.com/tools/SchematicViewer/SchematicViewer.html
6.101 Spring 2020 Lecture 4 37
After:
LTspice Secrets
Many aspects and functions of LTspice are not documented. You 
can learn lots of interesting undocumented capabilities of LTspice
from:
http://ltwiki.org/?title=Undocumented_LTspice
Of particular interest should be B-sources. These allow you to 
make devices such as non-linear resistors whose value is 
determined from a function of voltage, current, if statements, 
constants, etc. Though you cannot build these, they may be useful 
to model a part not available in LTspice, or to model a special 
function in your circuit you have not designed yet.
6.101 Spring 2020 Lecture 4 38
Questions??
6.101 Spring 2020 Lecture 4 39
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LTSPICE SHORTCUTS ON A MAC 
11/5/2013  REV 3 
 
a    DRAW CIRCLE 
b   BUS TERMINATION 
g   GROUND 
l   DRAW LINE 
s   ADD SPICE DIRECTIVE (right click for HELP ME EDIT) 
t   ADD TEXT COMMENT   
w   DRAW BOX 
 
z  H  HIDE LTSPICE 
z  L  SPICE LOG 
z  N  NEW SCHEMATIC 
z  O  OPEN 
z Q  QUIT LTSPICE 
z  S  SAVE 
z  Z  UNDO 
⇧z Z  REDO   
z  M  MINIMIZE 
⌥z M  MINIMIZE ALL 
z  W  CLOSE 
⌥z W  CLOSE ALL 
z  P  PRINT 
⇧z P  page seupt 
 
 
F2   COMPONENT 
F3   WIRE 
F4   NET NAME 
F5   DELETE 
F6    DUPLICATE 
F7   MOVE (CNTRL-R to rotate, CNTRL-E to mirror) 
F8   DRAG  (CNTRL-R to rotate, CNTRL-E to mirror) 
F9   UNDO 
⇧F9   REDO 
 
SPACE BAR   ZOOM TO FIT 
2 FINGER PINCH  ZOOM IN 
2 FINGER SPREAD ZOOM OUT 
 
 
Here are the modifier key symbols you may see in OS X menus: 
z  COMMAND 
⌥  ALT OR OPTION 
⇧  SHIFT