4.2 Adding Instances and Wires
To add an instance of a transistor, power supply, or other component to your circuit, use the Add Instance
dialog. You can access it in the menu Create > Instance; through the Create Instance button in the
toolbar (the transistor with the green plus by it); or by using the shortcut i .
Basically all instances we will need for this class can be found in analogLib. Select that as the Library,
then you can select the cell you want to add. Here are a few useful ones for this class:
• nmos4 - An NMOS device with the body terminal explicitly shown. Use this whenever you want an
NMOS transistor in your circuit. Set the Model name to NMOS , then set the Width and Length
as desired. The minimum length is 240nm, but most HW assignments will tell you what length to use.
• pmos4 - A PMOS device. It has the same fields as nmos4, except that you should set the Model
name to PMOS .
• vdc - A DC voltage source. You can set the DC voltage field to set the DC voltage. You can also
use this as an AC voltage source by setting the AC magnitude field. Note that if you use it as an
AC voltage source, it produces a small signal that doesn’t change any bias points - it’s not a number
of volts it applies.
• vpulse - This is useful for transient simulations. Set the Voltage 1, Voltage 2, Period, Rise time,
Fall time, and Pulse width as needed
• idc - A DC current source. Has the same fields as vdc, but is in amps rather than volts
• gnd - Represents ground. You will need at least one in your circuit if you’re going to run a simulation.
• vdd - Represents V
DD
. Note that it does not provide any power by itself - you will still need to connect
it to a DC voltage source. See the circuit in the example project to see how to use vdd.
• cap - A capacitor. Set the Capacitance field.
• res - A resistor. Set the Resistance field.
• vcvs - A voltage controlled voltage source. Set the Voltage gain field. You may also want to set the
Maximum Output Voltage and Minimum Output Voltage fields to make sure the output isn’t
higher than V
DD
or lower than ground.
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