Question

1. Design a "AC Voltmeter using Non-Linear Circuit using PSpice software. Explain the design process and components used for the design.

Answer 1

In this mode you will be looking at the ac signals and using the results to determine the ac gain of the circuit.

You will use the circuit shown in the following schematic.

V2 24Vdc 24Vdc RC 4.3k Rb 560k Cout HA MAG = OK PHASE = OK MAG = OK PHASE = OK Vout 10uF Rs Cin TVs Rs RL th 10uF 2.7k Q2N2222 1m Vac OVdc SOM

For the voltage source V1, use the VAC part. The VSIN part is used for the Transient Analysis simulations.

Note the use of a new symbol: In the Part menu, this is listed as VPRINT1 (in the SPECIAL library). This symbol is used to tell PSpice that you wish to include some characteristics of this node in your output file.

Double-left clicking on the symbol will bring up the Properties Editor screen.

Under the column designated AC enter OK. Under the columns designated MAG and PHASE, enter OK. Continue entering OK under any other characteristic that you wish to examine and record. You don’t have to enter OK as I have. Entering anything will activate the property.

If you wish to display the name and/or the value of the characteristic on the schematic, as shown on the input node Vs, highlight the column and press the Display... button.

The following screen will appear:

Display Properties Name: MAG Font Arial 7 Value: OK Change... Use Default Display Format Color Default Do Not Display Value Only Name and Value Name Only Both if Value Exists Rotation 180° 270 90° OK | Cancel Help

Here you can make your choices for displaying the symbol properties.

To start the simulation process, open the PSpice menu. The first choice available is New Simulation Profile. Left-click on it and the following window will appear.

Give the New Simulation a Name. For this example, use “ac Gain”. Left-click Create and the next screen will appear

New Simulation Name: Create Cancel Inherit From: none Root Schematic: SCHEMATIC1

Simulation Settings - ac Gain General Analysis Configuration Files Options Data Collection Probe Window Analysis type: AC Sweep/Noise - AC Sweep Type Linear Logarithmic Decade Start Frequency: 1kHz End Frequency: 1kHz Total Points: 1 Options: General Settings Monte Carlo/Worst Case Parametric Sweep Temperature (Sweep) Save Bias Point Load Bias Point Noise Analysis Enabled Output Voltage: IW Source Interval: -Output File Options Include detailed bias point information for nonlinear controlled sources and semiconductors (.OP) OK Cancel Apply Help

Choose the AC Sweep/Noise under the Analysis type option. Since in this example we will be looking at only one frequency, (i.e. 1kHz) set the AC Sweep Type as shown above. Under the Probe Window uncheck the Display Probe Window setting.

Run the simulation and open the output file (either using the shortcut icon on the left side or under PSpice, and View Output File). At the end of the output file you will find the AC Analysis results, a portion of which is shown below.

**** AC ANALYSIS TEMPERATURE = 27.000 DEG C ******************************************************************************

FREQ VM(VOUT) VP(VOUT) 1.000E+03 2.798E-03 -1.789E+02

**** 12/31/06 23:08:44 ******** PSpice Lite (July 2006) ******* ID# 10813 ****
** Profile: "SCHEMATIC1-ac Gain" [ F:\Orcad Capture CIS, Release 15.7\ac example-pspicefiles\schematic1\ac gain.sim]

**** AC ANALYSIS TEMPERATURE = 27.000 DEG C

****************************************************************************** FREQ VM(VS) VP(VS)

1.000E+03 1.000E-03 0.000E+00

In this example, the frequency (FREQ), magnitude (VM) and phase (VP) are displayed for the output signal node (Vout) and the input signal node (Vs).

Recall that for your reports, you can modify, add to, or delete anything from the output file, just as you would with a text file (which it is). Hence we could calculate the ac gain and include it in the simulation report.