0 Members and 1 Guest are viewing this topic.
The LM399 give out some 7 V. So it would need some precision divider with a factor of about 0.71. There is no need to go up to 10 V first. However this is not a very common divider ratio. There may be approximate values from some resistor arrays.
LM399 * 3/4 = 5.2V
Quote from: imo on April 24, 2019, 09:06:51 pmLM399 * 3/4 = 5.2Vdid you ever test the cirquit in real life?Up to now I have only simulations in LTSPICE.
Attached picture shows my way of getting nominal 5V.I mentioned it in a separate post previously. https://www.eevblog.com/forum/metrology/lm399-based-2-5v-reference/msg2319243/#msg2319243The tempco is roughly 1ppm/K. Long term stability not tested.
The tempco itself of the 50k 10turn pot is not important imho, the matching tempco between the 2 portions of the pot does.. What could be a matching tempco of such A and B parts of the pot?
Btw, in the simulation there are ripples of about 40uVpp (it is to expect), thus additional filtering would be nice to have. With 1uF the ripple is 50uVpp.PS: the "Branadic's" ripple is lower, around 17uVpp..
Quote from: ycui7 on April 25, 2019, 09:17:12 amAttached picture shows my way of getting nominal 5V.I mentioned it in a separate post previously. https://www.eevblog.com/forum/metrology/lm399-based-2-5v-reference/msg2319243/#msg2319243The tempco is roughly 1ppm/K. Long term stability not tested.Interesting. You have managed to get 2.5V reference from LM399 - I saw it in another post.Would you please post the full schematic - LM399 (~7V) - 5V - 2.5V?