DFTG 2419 Intermediate CAD
Student Guide
THE OPERATIONAL AMPLIFIER
ELECTRONIC SCHEMATIC
Figure 1. Operational Amplifier Package
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Student Guide
This project involves working with attributed blocks, dynamic blocks, tool palettes, and
DWFs. You are to create two drawings: the first contains a library of attributed blocks,
some with dynamic properties, and the second contains the schematic for an electronic
component called an operational amplifier, or op-amp (See the sketch in Figure 1).
According to the online encyclopedia Wikipedia,
(http://en.wikipedia.org/wiki/Operational_amplifier), an op-amp is a DC-coupled highgain electronic voltage amplifier with differential inputs and, usually, a single output. Opamps are among the most widely used electronic components; they are included in a vast
array of consumer, industrial, and scientific devices. Figures 2 and 3 display examples of
op-amps packaged several different ways.
Figure 2. A 741 op-amp in a metal can package
Figure 3. Op-amp ICs in 8-pin packages
DEFINE ATTRIBUTED BLOCKS
To begin the first drawing, open the drawing named Op-Amp Symbols.dwg from the Unit 2
folder in the Shared directory. Re-save it to your User folder with the same drawing
name.
Step 1: Define the attributes
• For each symbol in the drawing, define the attributes shown in Table 1 below.
• Invoke the ATTDEF command once for each tag. Remember to uncheck the Lock
position in block setting in the Attribute Definition dialog box.
• Provide the following settings for each attribute:
o Set the justification to Left.
o Set the text style to Arial.
o Set the text height to 0.2.
o Set the rotation angle to 0.
• Position each attribute next to the corresponding geometry.
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Table 1. Operational Amplifier Attributed Block Descriptions
Symbol
Block name
Resistor
Capacitor
Tag
Prompt
Default
REF
Reference designation
R1
OHMS
Resistance
1K
REF
Reference designation
C1
CAP
Capacitance
Dot
No attributes
NPN Transistor
REF
Reference designation
Q1
PNP Transistor
REF
Reference designation
Q1
Step 2: Define the blocks
Set a Node Osnap. Invoke the BLOCK command and make each symbol into an
attributed block.
• Specify the block names shown in Figure 4 below.
• To make it easy to align the blocks with the circuit lines, set the base point for each
block to the point shown in Figure 4.
• Select the attribute tags along with the block geometry in the order in which you want
to be prompted for the values.
• The points and the text are on a locked layer, so you do not inadvertently select them
when you make the blocks.
Remember the mnemonic for the transistors:
NPN = “Not Pointing iN”
PNP = “Point iN Please”
Figure 4. Base points for blocks
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Add a flip grip to each of the two
transistors as you did in the earlier
exercise (see Figure 5).
Step 3: Save the drawing
Re-save this drawing in your User folder
as Op-Amp Symbols.dwg.
Figure 5. Adding flip grips to the transistor blocks
DRAW THE OP AMP
You draw the schematic in a new drawing, and import the blocks from your Op-Amp
Symbols drawing with DesignCenter.
Step 1: Drawing setup
• Start a new drawing based on acad.dwt. Save this drawing in your User folder and
name it Op Amp.dwg.
• Create the layer configuration shown in Table 2 below.
Table 2. Layer Configuration information
NAME
Border
Circuit
Symbols
Text
Viewport
Xref
COLOR
White
Green
Red
Green
Magenta
Default
LINETYPE
Continuous
Continuous
Continuous
Continuous
Continuous
Continuous
LINEWEIGHT
.60mm
.30mm
.30mm
.30mm
Default
Default
PLOT
No
No
Step 2: Create a Tool Palette of Attributed Blocks
• Open DesignCenter if it is not already on your screen.
• Navigate to your User folder and find your Op-Amp Symbols.dwg drawing.
• Select the Blocks category.
• Drag a window around the icons for the five blocks you created in this drawing.
• Right-click on any selected block and choose Create Tool Palette from the shortcut
menu.
• Right-click on this new palette and choose Rename Palette from the shortcut menu.
Rename the new palette Op-Amp Blocks.
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Return to DesignCenter.
Expand the Textstyles category. Drag the Arial text style from DesignCenter and drop
it into your drawing. Drop down the list of text styles in the Annotate → Text ribbon
panel (or the Styles toolbar) and set the Arial text style current.
Export your tool palette. Save it in your User folder in a file named Op-Amp.xtp.
Step 3: Draw the circuit
• When you are finished importing the blocks, set the Xref layer current.
o To help you, copy the drawing named grid
underlay.dwg from the Unit 2 folder in the Shared
directory to your User directory.
o XREF your copy of this drawing into your Op Amp
drawing at point 0,0,0.
o Freeze all the layers in the XREF except the layer
named grid-2.0. (Remember that XREF layers have a
vertical bar | in the name.) Do not freeze any other
layers.
o Invoke the XCLIP command and clip out a square
that is 24 units on a side, Your drawing should look
similar to Figure 6.
Figure 6. Grid lines for circuit
Lock your Xref layer.
o Click on the Home ribbon tab.
Click on the panel separator in
the Layers panel to expand it.
As shown in Figure 7, set
Locked layer fading to 70% or
more. Fading the grid lines
makes it easier to distinguish
them from your circuit lines.
o
Figure 7. Locked layer fading for the Xref layer
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Do not draw the circuit as it appears in Figure 1. Instead, apply the rules shown in the
Guidelines for Drawing Electrical Schematics section earlier in this unit. For
example, straighten circuit lines where possible to make the schematic easier to read.
o If you wish, print the Printable grid.pdf file, available in Blackboard and also in the
Unit 2 folder of the Shared directory.
o Draw the circuit on this grid before you start drawing in AutoCAD.
When you are ready, set the Symbols layer current and insert the electronic component
blocks to create the circuit. To insert a block from the palette, click on the block icon
in the palette and then click on the insertion point in the drawing. Follow the
schematic as you work.
Set the Circuit layer current and draw the circuit lines, tracing over the grid lines.
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Remember to re-number the components in the final drawing from left-to-right and
top-to-bottom.
The small labeled circles correspond to pins on the chip. The numbering of these
circles does not change in the finished schematic. The diameter of the small labeled
circles is 0.125.
Step 4: Create a layout
• Set up a layout named Op-Amp that displays your drawing:
• You can rename Layout1 if you wish.
• Open the Page Setup dialog box and create a named page setup with the following
settings:
ο Set the Printer to DWF eView (A&E).pc3.
ο Set the Paper size to DWF ANSI B (17.00 x 11.00 Inches).
ο Set the Plot Style table to monochrome.ctb.
• If AutoCAD does not supply a viewport on this layout, invoke the VPORTS
command and insert one. Make sure the viewport is on the Viewport layer so it will
not print.
• Enter Mspace and pan and zoom as necessary to arrange your drawing in the
viewport. Turn off the grid by freezing the layer named grid underlay|grid-2.0 in this
viewport.
• Return to Pspace and re-size the viewport as necessary to make it show the circuit.
There is no scale for this drawing — make it fill the page.
• Set the Border layer current and draw a border.
• Re-open DesignCenter and import your Mechanical title block from Title Blocks.dwg.
ο Post the File menu and choose Drawing Properties…. Enter your name or initials in
the Author box on the Summary tab. Click OK to close the dialog box.
ο Fill in the rest of the title block.
• Add the notes shown in Figure 1. The text height is 0.15.
Step 5: Publish the drawing
• Save your drawing.
• Invoke the Publish command, and publish your drawing as a single-sheet DWF.
• Submit the DWF as directed by your instructor.
• When your instructor returns a graded version of your DWF, save it to your User
directory.
• Open your drawing.
• Click on the View ribbon tab, and then the Markup Set Manager button on the Palettes
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panel
to display the Markup Set Manager palette.
Open the graded DWF returned by your instructor.
If necessary, make corrections and re-publish your DWF.
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