Electronics > Beginners
zener reference instability
nnills:
I put the breadboard in a esd bag with some foam in the opening(to stop airflow). It is now stable to 100 uV!(over 1 hour) :)
iMo:
Have you coupled the zener and the transistor thermally?
Andreas:
--- Quote from: imo on March 11, 2019, 04:49:02 pm ---It looks like the LM358 does not like that wiring :)
--- End quote ---
No Op-Amp likes 100nF (C3) across the output without furhter measures.
(see my LTZ1000 cirquit with a additional series resistor for the negative input and a additional capacitor from Output to negative input of the OP)
--- Quote from: imo on March 11, 2019, 06:50:44 pm ---Have you coupled the zener and the transistor thermally?
--- End quote ---
Even then there will be some T.C.
For a good compensation between zener and VBE you will have to increase the zener voltage to 5.6-6.2 (around 5.9) V
with best regards
Andreas
IconicPCB:
What Andreas said ...
Go with a slightly higher zener voltage and then insert a low value resistor ( in the order of tens of ohms between the zener and the transistor base.
Adjust the resistance for prefered zero tempco temperature ( say room temperature?)
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