I have a schematic that has the intersected circles that IMOD and IBIAS arrows point to and I wonder about its meaning

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if I know that this symbol is a current sink ..how can the Control IC change the current passing through the LD ? and how can I relate the resistor connected to IMODN to current in LD ?


That is a symbol for a current, usually accompanied by an arrow to denote direction.Based on the fact that it is grounded, it can be inferred it is a sink. The naming IMOD suggests it is also adjustable by the internal logic of the IC.

  • \$\begingroup\$ if you know that this ADN2848 is used to drive a laser diode how can you interpret the direction of current ? I mean how the adjustable current from the Control IC change the current into LD ? \$\endgroup\$ – Omar Ayman Jun 15 '17 at 1:10
  • \$\begingroup\$ The current flows from top to bottom in the diagram. \$\endgroup\$ – The Photon Jun 15 '17 at 1:33
  • \$\begingroup\$ Concur, because below it is a flat line indicating the lowest voltage in the gradient. Probably a ground or maybe just a pcb trace of that shape. \$\endgroup\$ – SDsolar Jun 15 '17 at 1:36
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    \$\begingroup\$ Minor comment - the two NPN transistors are not a current mirror. They are a differential pair used to switch whether the modulated current comes from the laser diode (LD) or from the IMODN pin that just has a dummy resistor in this case. \$\endgroup\$ – Kevin White Jun 15 '17 at 2:11

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