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Low Speed and Low Power Amplifiers |
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Research Assignement Answers |
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| Q: |
What is the problem caused when using a resistor divider style rail-to-rail op amp? What rail-to-rail input architecture is preferable? Why? |
| A: |
The resistor divider style rail-to-rail op amp causes higher noise and drift than the Dual NPN/PNP input stage. The Dual NPN/PNP input stage doesn't have resistive dividers, which attenuate the signal and are the cause of the higher noise and drift. See LMV931 datasheet. |
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| Q: |
What is the definition of slew rate? |
| A: |
The maximum rate of change of the output signal which the amplifier is capable of delivering. See AN-71 Application Note or Knowledge Base with keyword: slew rate. |
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| Q: |
Use the LMV931 datasheet to find the typical slew rate under the AC Electrical Characteristics rated at 2.7V. Use this slew rate and maximum output voltage to determine Full Power Bandwidth (round to nearest mW). |
| A: |
Slew Rate = 0.4 V/uS, using equation 12 from AN-71, the maximum power is 24mW. See AN-71 Application Note. (Eq. 12) |
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| Q: |
What is the definition of "Common Mode Range"? |
| A: |
This graph is not found in most high voltage parts because they rairly have rail-to-rail inputs. The low voltage, low power op-amps have two different offset voltages in some parts due to their rail-to-rail inputs. This is something to be aware of when designing a circuit. See LMV931. |
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| Q: |
Use the LMV931 datasheet to look at the graph of Offset Voltage vs. Common Mode Range. What is different about this graph compared to most high voltage operational amplifiers? |
| A: |
This graph is not found in most high voltage parts because they rairly have rail-to-rail inputs. The low voltage, low power op-amps have two different offset voltages in some parts due to their rail-to-rail inputs. This is something to be aware of when designing a circuit. See LMV931. |
