ECE 191: Project 11 Winter 2004

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ECE 191 Project 11Winter 2004

• Breakout Box for Testing High Voltage Operational
  Amplifier
• Sponsor SPAWAR
• Mentor Eric Noel Cartegena
• Members David Kruidhof
• Jesse Ghassan
• William Su

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Agenda

• Gantt chart
• Tasks and accomplishments
• Circuit board progress
• Testing of current board
• Values obtained
• Problems
• Solutions
• Design of new board
• Summary

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Gantt Chart
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Tasks and Accomplishments

• SPAWAR visit
• Begin testing circuit board (David, Will)
• Presented preliminary board designs to mentor
  (Jesse)
• Researched op amp test board design (Jesse)

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Testing of Circuit 1

• Circuit 1 tests for
• Input Offset Voltage
• Input Bias Current
• Input Offset Current
• Power Supply Rejection Ratio
• Common Mode Rejection Ratio
• All tests done on a UA741 op amp

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Circuit 1
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Input Offset Voltage (VOS)

• Definition the voltage that must be applied
  between the two input terminals of the op amp in
  order to obtain zero volts at the output.
• Our AUT (Amp Under Test) had a VOS of .501mV
• Maximum VOS from spec sheet is 5mV

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Input Bias Current (IB/-)

• Definition the average amount of current that
  enters or leaves the op amps input terminals.
• Our IB 35.9nA, IB- 34.9nA
• Max IB 80nA

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Input Offset Current (IOS)

• Definition the difference between the input base
  currents. IOS is typically ten times less than
  the IB.
• Our IOS .4nA
• Max IOS 8nA

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Power Supply Rejection Ratio (PSRR)

• Definition the ratio of the power supply voltage
  change over the output voltage change. This
  provides a measurement of how the ripples in the
  power supply affect output of the op amp.
• This test is not suitable for measuring the PSRR
  as a function of frequency because the power
  supplies were changed in the form of step inputs,
  rather than attaching an AC signal.
• Our PSRR 112.04dB, PSRR- 107.33dB
• Max PSRR 90dB

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Results

• Ours
• VOS .501mV
• IB 35.9nA
• IB- 34.9nA
• IOS .4nA
• PSRR 112.04dB
• PSRR- 107.33dB

• Max Pass?
• 5mV Yes
• 80nA Yes
• 80nA Yes
• 8nA Yes
• 90dB Yes
• 90dB Yes

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Existing Board Problems

• Current board design supplies a single power
  supply voltage to all onboard op amps.
• This includes both the AUT along with the onboard
  op amps.
• SPAWAR requires testing op amps with a variety of
  power supply voltages.
• Board must allow any op amp pin configuration to
  be tested.

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Solutions

• Use a male pin header type configuration to allow
  universal op amp input pin configurations.
• Terminate the six input leads with a single pin
  for each.
• Wired jumpers will be used to connect the pins
  together.

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Solutions

• Add two additional coaxial power supply inputs
  to the board.

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Future Plans

• Complete op amp tests on test board
• Add a ground connection to the breakout box.
• Learn Protel to begin drawing up PCB board
  diagrams
• Next weeks presentation
• More circuit board results
• More on the board design

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Summary

• Circuit Board Testing Progress
• Values from testing circuit 1
• Problems encountered
• Solutions