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Published byJessica McClure Modified over 3 years ago

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1 Improved Howland Current Pump Stability Tim Green Senior Analog Applications Engineers Precision Analog Linear Applications July 19, 2013

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2 Improved Howland Current Pump IL Accuracy Circuit RT allows for trim to optimum Z OUT and improved DC Accuracy Ideal Op Amp

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3 Improved Howland Current Pump V-I DC Accuracy Calculations 1% Resistors (w/RT=0) could yield only 9% Accuracy at T=25°C Still useful for V-I control in Motors/Valves V-Torque Control Outer position feedback adjusts V for final position

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4 Improved Howland Current Pump Simplified Equation

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5 Improved Howland AC Analysis Op Amp sees differential [(-IN) – (+IN)] feedback = (Must be positive number else oscillation!) RF RI

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6 Improved Howland AC Analysis + -

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7 Improved Howland 1/ Plot - Full Load

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8 Improved Howland 1/ Calculation No Load & Full Load ILROfzfp DC 1/ Hi-f 1/ No Load0A Hz31.83kHz17.62dB77.17dB Full Load1A Hz31.83kHz19.45dB77.15dB Change in RO from No Load to Full Load has no significant impact on the 1/ Plot

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9 Improved Howland Tina Transient Analysis Circuit RF RI

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10 Improved Howland Tina Transient Analysis Results

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11 Improved Howland Modified 1/ for Stability

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12 Improved Howland AC Analysis Final Design for Stability RF RI

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13 Improved Howland AC Analysis 1/ - Final Design for Stability fcl

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14 Improved Howland AC Analysis Loop Gain - Final Design for Stability fcl

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15 Improved Howland AC Transfer Analysis IL/VIN - Final Design for Stability RF RI

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16 Improved Howland AC Transfer Analysis IL/VIN - Final Design for Stability

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17 Improved Howland Transient Analysis IL/VIN - Final Design for Stability RF RI

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18 Improved Howland Transient Analysis IL/VIN - Final Design for Stability

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