Difference between revisions of "Hardware:GPA"
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| − | The gradient amplifier is used to supply the current to the gradient coils. Since it's the fields we care about, and the fields are proportional to current, this amplifier can be viewed as a voltage to current transducer; it takes a voltage waveform from the console and creates a current proportional to that voltage in the gradient coil. It is similar to a common audio power amplifier except that it must also be able to output DC currents. It uses two [http://www.ti.com/lit/ds/symlink/opa549.pdf OPA 549] power op-amps in a bridged configuration. A current sense resistor is used to compare to the input voltage to ensure that the current itself is proportional to the | + | The gradient amplifier is used to supply the current to the gradient coils. Since it's the fields we care about, and the fields are proportional to current, this amplifier can be viewed as a voltage to current transducer; it takes a voltage waveform from the console and creates a current proportional to that voltage in the gradient coil. It is similar to a common audio power amplifier except that it must also be able to output DC currents. It uses two [http://www.ti.com/lit/ds/symlink/opa549.pdf OPA 549] power op-amps in a bridged configuration. A current sense resistor is used to compare the output current to the input voltage to ensure that the current itself is proportional to the desired signal. A current sensor is created by measuring the voltage across a small resistor in series with the output. |
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Revision as of 23:59, 13 August 2013
Gradient Power Amplifier
The gradient amplifier is used to supply the current to the gradient coils. Since it's the fields we care about, and the fields are proportional to current, this amplifier can be viewed as a voltage to current transducer; it takes a voltage waveform from the console and creates a current proportional to that voltage in the gradient coil. It is similar to a common audio power amplifier except that it must also be able to output DC currents. It uses two OPA 549 power op-amps in a bridged configuration. A current sense resistor is used to compare the output current to the input voltage to ensure that the current itself is proportional to the desired signal. A current sensor is created by measuring the voltage across a small resistor in series with the output.
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