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This README created 3.31.2003
--------------------- Contents of directories -----------------------
This directory holds the schematics and associated materials for a
SPICE model of Agilent's MSA-2643 bipolar amp. The model was obtained
from Agilent's datasheet 5980-2396E. The directory structure is as
follows:
RF_Amp (base directory)
MSA-2643.sch -- schematic of stuff inside device package (as shown in
p. 7 of datasheet. Note that I have not included the transmission
lines in this schematic because no value of Z was included in the data
sheet. (Yes, it's probably 50 ohms, but including them was a
sideshow compared to my main intent: build a hierarchical model of an
RF circuit.)
MSA-2643.cir -- netlisted circuit ready for SPICE simulation.
Q1.sch -- schematic model of Q1 MSA-26 transistor shown on p. 8 of datasheet.
Q1.cir -- netlisted circuit holding .SUBCKT model of Q1.
Q2.sch -- schematic model of Q2 MSA-26 transistor shown on p. 8 of datasheet.
Q2.cir -- netlisted circuit holding .SUBCKT model of Q2.
README -- this file.
Simulation.cmd -- a file holding SPICE analysis commands which is read
at simulation time by the SPICE simulator.
5980-2396E.pdf -- Agilent datasheet about the MSA-2643.
./model/
BJTM1_Q1.mod -- text-based SPICE model of BJT1 used in Q1 .SUBCKT
DiodeM1_Q1.mod -- text-based SPICE model of diode M1 used in Q1 .SUBCKT
DiodeM2_Q1.mod -- SPICE model of diode M2 used in Q1 .SUBCKT
DiodeM3_Q1.mod -- SPICE model of diode M3 used in Q1 .SUBCKT
(similar files for Q2 models. . . .)
These models were obtained from parameters give in p. 8 of the datasheet.
./sym/
BJT_Model.sym
Q_Model.sym -- symbol pointing to lower level models placed on upper
level schematic.
Other symbols from stock library used in this example's schematics.
------------ Usage of hierarchical SPICE models ---------------------
This project exemplifies construction of a hierarchical SPICE
simulation using Lepton EDA. The project is built in the following way:
1. Use a text editor to create .mod files containing SPICE models of
the transistors and diodes on p. 8 of the datasheet.
2. Create Q1 and Q2 transistor model schematics using lepton-schematic.
Place the .SUBCKT SPICE block on the schematic to alert the netlister that
the schematic is a lower level .SUBCKT for incorporation into other
schematics. Place spice-IO pads on the schematic to instantiate the
IOs. Make sure to number the spice-IO pads in the same order as you
wish them to appear in the .SUBCKT line in the .cir.
3. Generate the .SUBCKT netlist by saying:
lepton-netlist -g spice-sdb -o Q1.cir Q1.sch
lepton-netlist -g spice-sdb -o Q2.cir Q2.sch
4. Create a symbol for Q1.cir and Q2.cir which will be dropped onto
the higher lever schematic. Name the symbol Q_Model.sym. Set the
symbol "DEVICE" attribute = NPN_TRANSISTOR_subcircuit. This causes
the netlister to use "write-default-component" to write out the SPICE
line for the component. Make sure that the "REFDES" attribute is X?
and not Q? -- this enables the .SUBCKT file to be attached to the
device.
5. Create the higher layer schematic MSA-2643.sch. Place
two copies of Q_Model.sym onto the schematic, corresponding to Q1 and
Q2. Make Q1 point to its model by setting the following attributes:
model-name: Q1_MSA26F
file: Q1.cir
Do the same for Q2.
6. Create the rest of the higher layer schematic the usual way. Make
sure to place a spice-include block on the schematic and point it to
"Simulation.cmd". Place any analysis commands (e.g. dc, ac, tran,
etc.) into the file "Simulation.cmd".
7. Netlist the higher layer design:
lepton-netlist -g spice-sdb -o MSA-2643.cir MSA-2643.sch
8. The circuit may be simulated by any desired SPICE simulation
and analysis package, e.g. ngspice.
Stuart Brorson
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