This circuit is from the datasheet of the famous LTZ1000 voltage reference:
Can anyone explain in detail how the circuit works? Especially the 400 kΩ effect; what is the benefit of the 400 kΩ resistor?
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It provides temperature stability to meet the 0.05ppm/°C Drift specification. Source: page 5 of the datasheet.
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\$\begingroup\$ I checked page 5 of the datasheet and could not find where it explains that the 400k ohm resistor provides the temperature stability to achieve the 0.05 ppm/°C drift. \$\endgroup\$ Commented Feb 6 at 17:34
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\$\begingroup\$ From page 5, first line under the schematic: "*PROVIDES TEMPERATURE COMPENSATION, DELETE FOR LTZ1000A". The "0.05 ppm/°C drift" comes from the device specification. The resistor is how you achieve that. \$\endgroup\$– MOSFETCommented Feb 6 at 17:37
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\$\begingroup\$ Apart from achieving the "0.05 ppm/°C drift", does the absence of the 400kΩ resistor affect the 7.02V voltage to be generated by the LTZ1000 reference? \$\endgroup\$ Commented Feb 6 at 17:46
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\$\begingroup\$ @jsuarezbaron IDK and I don't have time to look into it. But without even thinking about it, why wouldn't you include it without out any thought? I guess if your in the quantities of > 10 million's, shaving off an SMD resistor might be worth the increased temp drift... \$\endgroup\$– MOSFETCommented Feb 7 at 16:00