Difference between revisions of "Hardware:GPA"
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[[File:GPASchematic.jpg|600px|thumb|right|figure 1. so and so]] | [[File:GPASchematic.jpg|600px|thumb|right|figure 1. so and so]] | ||
| − | 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 sensors compares the output current to the input voltage to ensure that the current itself is proportional to the desired signal. | + | 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 sensors compares the output current to the input voltage to ensure that the current itself is proportional to the desired signal. The current sensor consists of an [http://www.ti.com/lit/ds/symlink/ina105.pdf INA105] differential amplifier that measures the voltage across a small resistor in series with the output. |
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Revision as of 00:01, 14 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 sensors compares the output current to the input voltage to ensure that the current itself is proportional to the desired signal. The current sensor consists of an INA105 differential amplifier that measures the voltage across a small resistor in series with the output.
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