Lab 02
Introduction to Pspice

Hung, Bill Chun Wai

__Objectives__

To get
familiar CAD software Spice, in particular, PSpice. To learn the basis of representing circuits.

__Procedure/Measurement
Report__

1. Perform a transient analysis with
PSpice on a RC circuit.

2. Perform a transient analysis with
PSpice on a RLC circuit.

3. Perform transient analysis with
various resistors

4. Perform a DC analysis with PSpice on a MOSFET circuit.

__Results/Analysis__

4.1 Lowpass filter Circuit

The
result of the circuit is shown in Figure 1. This is a lowpass
filter with the coupling capacitor. The coupling capacitor filters out the low
frequency because when the frequency is high, the coupling capacitor acts like
a voltage resistance voltage source. In other words, the coupling capacitor prevent the output voltage to change too rapidly.

In
return, the low frequency, pass the coupling because the capacitor is allowed
enough time to charge up or discharge.

4.1 Lowpass filter Circuit with Inductor

The H1 indicated
in the diagram above is the inductor of 100uH. The inductor is added to the
circuit will produce a ringing effect. In other words, the voltage across the
resistor oscillates because blow the voltage source side and the
inductor-capacitor side is offering voltage to the resistor.

However,
due to the small inductance used in the circuit, the oscillation of the circuit
is not obvious.

4.2 Lowpass filter with various resistors

The
resistor of value 1 led to an underdamp situation and
ringing occurred.

In this
part of the experiment, the resistors are replaced by 1 ohm, 50 ohm, 100 ohm,
200 ohm, and 665 ohm. As the resistance increase, the oscillation of the
circuit decrease. This is because the resistor acted as a damping force, and
when the resistance is larger, the damping force for the oscillation of the
circuit is larger. Thus, the oscillation is smaller when the resistance is
larger.

4.2 Lowpass filter with various resistors

The
MOSFET circuit shown above is a NMOS with parameters like kp=60e-6, Vto=1, and Lambda=0.05.

This
generates a I-V plot of a typical MOSFET circuit
indicated in Figure 4.

__Conclusions__

The lab is to be familiar with PSpice, particularly how to perform transient analysis, DC
analysis, and to generate I-V plots. The lab demonstrated the basic techniques
to stimulate a circuit and the response of a circuit.