ECE 220 PreLab

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ECE 220 Pre-Lab

• Lecture 2

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Where and When?

• Turn in to the stockroom
• Due at 400 pm on Friday
• Dont be late, it will hurt

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Outline

• Purpose of the lab
• What to turn in for each section
• Results you should expect
• Questions

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Purpose?

• Apply NVA (Node Voltage Analysis) and MCA (Mesh
  Current Analysis)
• Design a voltage/current meter
• Work with approximate DC model of a BJT
  transistor
• Build a transistor amplifier

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Part 1 Something like this
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Part 1 Turn in what?

• Calculation of voltages A, B, and C
• Calculation of currents i1 through i6
• Print-out of the simulated schematic
• Calculation of node voltages with the diode
  reversed
• Check with PSpice, but dont have to submit

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Part 1 What should I get?
Node A 15mA (A B)/130 (A C)/470
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Part 1 What should I get?

• For the last part, there is something you should
  know.
• If current is flowing from the point of the
  triangle to the fat end of the triangle in a
  diode the diode acts as an open circuit.
• Current cannot flow backwards through a diode.

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Part 1 What should I get?
This is the equivalent after reversing the diode.
Now, is NVA really the best approach now? Not
really. Current division, maybe?
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Part 2 Something like this
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Part 2 Turn in what?

• Calculations for the 3 mesh currents.
• Print-out of simulated schematic.

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Part 2 What should I get?
This is with the gain set to 150.
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Part 2 MCA Example
-10 1k(i1) 3k(i1 i2) 0 3k(i2 i1)
1k(i2) 1k(i2) 0 -10 4k(i1) 3k(i2) 0
3k(i2) 3k(i1) 2k(i2) 0 4k(i1) 3k(i2)
10 0 -3k(i1) 5k(i2) 0 Solve
the system and get i1 4.55 mA and i2 2.73 mA
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Part 3 Something like this
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Part 3 Turn in what?

• Circuit diagram and calculations for ammeter.
• Same for voltmeter.
• Calculations showing resistors as parallel/series
  combinations of standard resistor values.
• Calculation of your FSR error.
• Print-out of your probe plot.
• Print-out of schematic with correct R.
• Print-out of plot showing meter current vs. the
  input current.

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Part 3 What should I do?

• Ammeter and Voltmeter
• Figure out Rmeter
• Vfs / Ifs Rmeter
• Figure out R to give full-scale deflection
• For ammeter, R is in parallel
• For voltmeter, R is in series
• Find standard resistor values and try to combine
  them to get R for each meter
• It wont be perfect, get your error bounds based
  on tolerances and your realization error
• For PSpicefollow the directions closely
• Use their example as a guide

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Questions?

• The only stupid question is the one you did not
  ask!!!!

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Until Next Time

• Come see me during office hours if you need help.
• Send an email if you prefer.