Department of Electrical and
Computer Engineering
Electronics

Introduction to Electronics Workbench


Figure 1


Figure 2

This tutorial shows how to simulate a circuit using Electronics Workbench.

  • Fire up Mulitsim 8
  • Place components on the schematic.

    Ground   Every schematic needs a ground symbol. Use;

    Place > Component
    Choose:
  • Database: Master Database
  • Group: Sources
  • Family: Power_Sources
  • Component: GROUND
    • Hit OK and click on the desired location in the schematic window for the ground symbol.
    If you don't like the location, click on the symbol to select, and drag to a more appropriate spot.
    If you want more ground symbols, click to select and use: edit>copy and edit>paste to duplicate the symbol. (control_C and control_V work great for copy and paste.) Resistors   Use;
    Place > Component
    Choose:
  • Database: Master Database
  • Group:Basic
  • Family: RESISTOR
  • Component: 5.1K
    • Hit OK and place R1 on the schematic. Right click on the resistor to see placement options like rotate.

    Repeat, placing 51K, R2 and also, an additional 100 ohm resistor on the schematic. Op Amp   Here we are modeling the opamp as a voltage controlled voltage source with a gain of 100,000, an output impedance of 100 Ohms, and a high frequency bandwidth of 100 Hz.

    Place the voltage controlled voltage source. Use;

    Place > Component

  • Database: Master Database
  • Group:Sources
  • Family: VOLTAGE_CONTROLLED_VOLTAGE_SOURCES
  • Component: VOLTAGE_CONTROLLED_VOLTAGE_SOURCE
    • Double click on the voltage controlled voltage source to set the Voltage Gain (E) to 100000.

    Place capacitors needed to model the opamp high frequency rolloff.

  • Database: Master Database
  • Group:Basic
  • Family: Capacitor
  • Component: 10uF
    • Repeat adding a 6.2uF capacitor. A 16.2uF capacitor, together with the 100 Ohm opamp output impedance results in a 1.62 mSec RC time constant. This corresponds to a 1/1.62x10-3 rad/sec opamp bandwidth.
    1/RC = 1/1.62x10-3 = 617rad/sec = 2p98Hz
    This models am opamp with a 98Hz high frequency rolloff.

    Wire the circuit. Place the cursor on a terminal. It turns to a black dot. Click on the terminal. Move the cursor to another component terminal and click. This wires the two terminals together. Click on an intermediate point before clicking on the destination terminal and the wire will be constrained to pass through that point.

    Double click on the output wire. Label the output. Repeat for the input.

    Simulate

    Use;

    Simulate > Analysis > AC Analysis
    Set the frequency parameters to

  • Start Frequency; 100 Hz
  • Stop Frequency: 100 MHz

    • Select the output tab and set the "Selected variables for analysis" to $output.

    Hit the simulate button. The grapher window comes up. Click on the grid button.

    Right click on the magnitude axis. In the axis properties window select Decibels for the scale. Edit the left axis label, adding the units, dB. View full screen. Note that the inverting opamp circuit has a bandwidth of 1MHz even though the opamp only has a bandwidth of 100Hz. The gain-bandwidth product is a constant. 100,000 * 100Hz = 1E7 = 10 * 1MHz.