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eigenbau:bipolar_current_driver:start [2021/10/29 16:04]
mquensen created
eigenbau:bipolar_current_driver:start [2021/10/29 16:09] (current)
mquensen [Issue list]
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 ==== Schematic and layout ==== ==== Schematic and layout ====
-A OPA549 gives out some current that is send through some device (e.g. a coil) and finally a reference resistor. The voltage drop there is measured with an instrumentation amplifier. At an OPamp in PI-controller circuit is is compared to a setpoint signal and the difference signal is proportionally amplified and integrated over. The resulted voltage is now applied at the OPA549, in voltage follower circuit. The setpoint signal can be applied via BNC, and there is also the option to use a trimmer for a constant offset.+A OPA549 gives out some current that is send through some device (e.g. a coil) and finally a reference resistor. The voltage drop there is measured with an instrumentation amplifier. At an OPamp in PI-controller circuit it is compared to a setpoint signal and the "error signalis then proportionally amplified and integrated over. The resulted voltage is now applied at the OPA549, that is in non-inverting amplifier configuration. The setpoint signal can be applied via BNC, and there is also the option to use a trimmer for a constant offset
 + 
 +The OPA549 features a logic signal to shut it down, and a pin for setting a current limit. Both functions are implemented.
  
 The layout is designed as two boards. One for the control (reference resistor, PI OPamp, instr. amps ...) and the other for the OPA549. The layout is designed as two boards. One for the control (reference resistor, PI OPamp, instr. amps ...) and the other for the OPA549.
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   * There are too many pads for the output current. Not needed.   * There are too many pads for the output current. Not needed.
   * The PI-controller OPamp has a pin distribution that does not fit to its footprint, I think.   * The PI-controller OPamp has a pin distribution that does not fit to its footprint, I think.
 +  * There is no option to discharge the Elko's in the OPA549 board. They remain charged for quite some time after turning off the power supply.