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What is the dashed resistor symbol going to the ground shown in the picture?

Thank you.

enter image description here

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    \$\begingroup\$ Have you read the accompanying text? \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 21 '16 at 15:08
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    \$\begingroup\$ There's a nice * there and a nice note right there on your picture that tells you exactly what it means. There must be a galvanic path from Vin- to ground. That resistor represents that path. \$\endgroup\$ – jonk Oct 21 '16 at 15:08
  • \$\begingroup\$ A dashed symbol or wire normally means that the part is not always present in the circuit or that it can be left out under certain circumstances. In this case it's meaning seems to be that the resistor can be left out if V_IN- already has some specific properties. \$\endgroup\$ – Martin Rosenau Oct 21 '16 at 15:42
  • \$\begingroup\$ Vref needs an input bias path to ground proabably, which may or may not be provided whatever you put on Vin- \$\endgroup\$ – Voltage Spike Oct 21 '16 at 16:20
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For the 2.5V reference zener diode to be biased correctly (it needs a minimum current passing through it to produce an accurate 2.5 volts across it), there must be a dc current path to ground from Vref-.

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  • \$\begingroup\$ Thank you for the kind respnse, but what is the difference between the dashed resistor and a normal resistor? \$\endgroup\$ – Sodium Acetate Oct 21 '16 at 15:35
  • \$\begingroup\$ If you read the note, you must put a pull-down resistor to the ground at the Vref- input, i.e. you must present some DC impedance on this pin as it shouldn't be floating. \$\endgroup\$ – lucas92 Oct 21 '16 at 15:38
  • \$\begingroup\$ @SodiumAcetate the dashed lines imply that whatever source drives Vin, it must be dc coupled to ground in other words, the source has an internal resistance to ground and you can't (for instance) capacitively couple a source to that input. \$\endgroup\$ – Andy aka Oct 21 '16 at 15:48

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