Electronics > Projects, Designs, and Technical Stuff
Simple opamp circuit linearity problem
SilverSolder:
--- Quote from: Unixon on February 18, 2019, 07:40:43 pm ---
--- Quote from: SilverSolder on February 18, 2019, 07:17:15 pm ---Also - What is Vcc in this circuit - is it 5V?
--- End quote ---
All four resistors values in this configuration are heavily interlocked, I can't help it if they are the same order of magnitude for certain conditions.
--- End quote ---
Understood - I thought it was a "rule of thumb" design, but you are clearly way ahead of me here! I'm going to have a look at the book you linked, sounds interesting.
Best regards -
Unixon:
Hi,
I found another problem with this circuit. LMV321 based voltage follower for TL431 reference consistently produces about -375mV output offset on multiple boards. This offset looks weird considering the gain and absence of any huge resistance in feedback loop or at an input. What's going on?
Last time I tested this receiver by directly providing an input voltage from a signal generator and the output was close enough to expected signal so I didn't even notice this offset. Then I went to testing this circuit against different current loop drivers and found this offset while trying to get voltage-current-voltage double conversion work as precisely as possible for this circuit and an isolated loop driver built on HCNR201 linear optocoupler with TSX561A op amps (the driver schematic is from HCNR201 datasheet/app.note). This isolated driver is a bit off by itself, but it looks like the receiver is also responsible for inserting additional offset into signal by shifting the reference voltage.
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