Electronics > Projects, Designs, and Technical Stuff
Voltage boosting an opamp
Yansi:
Not saying it was unstable, but it just got me thinking how or if it could be improved right away.
Your suggestion does make sense, that way the tempco of those two Vbe get compensated. However what about those two voltage controlled current sources? There are still those -2mV/K, i.e. 0.002V/100ohm = 20uA/K drift. Which if I understand correctly will make a change of 1mA in bias @50K temperature difference, which is not that nice.
Hopefully the calculation can be done that way - taking the tempco of the PN junction divided by the Re of the current source - considering constant voltage at the base. (decreased Vbe means increased Re voltage, hence increased current).
magic:
Almost correct, although in principle you should also account for intrinsic emitter resistance. That's the inverse of transconductance: how many mV ΔVbe per 1mA ΔIc. In a VCCS circuit, rE adds to your emitter resistor, for relatively obvious reasons.
That being said, transcondutance at collector current Ic is approx Ic/30mV, depending on die temperature. So your rE is a few ohms, quite insignificant.
macboy:
--- Quote from: Yansi on November 10, 2019, 05:42:50 pm ---Your solution is the same type, as if you would just say "buy a complete ready test instrument for the purpose", why making one. No thanks.
Now I politely ask you to leave this thread, as you did not contribute anything useful, rather just being provocative and nitpicking about what is or isn't expensive, which is not the topic this thread is about. Neither are you entitled to evaluate how much work something required to make. This is my thread and I make the rules.
Thank you for making mess out of this thread, no-one will be willing to read. Please leave. Bye.
--- End quote ---
It most certainly is not your thread just because you started it, and you do not make any rules in this forum.
Simon:
--- Quote from: Yansi on November 10, 2019, 05:42:50 pm ---Your solution is the same type, as if you would just say "buy a complete ready test instrument for the purpose", why making one. No thanks.
Now I politely ask you to leave this thread, as you did not contribute anything useful, rather just being provocative and nitpicking about what is or isn't expensive, which is not the topic this thread is about. Neither are you entitled to evaluate how much work something required to make. This is my thread and I make the rules.
Thank you for making mess out of this thread, no-one will be willing to read. Please leave. Bye.
--- End quote ---
Now I will politely ask you to leave this forum if this is the way you intend to conduct yourself! you don't own the thread oh powerful one so I have locked it, SO THERE!
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