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 Forum index » DIY Hardware and Software
Tying together opamp outputs?
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AlanP



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PostPosted: Tue May 11, 2021 12:39 am    Post subject: Tying together opamp outputs? Reply with quote  Mark this post and the followings unread

http://jhaible.com/legacy/frequency_shifter_fs1a/jh_fs1a_schematics_board_2.pdf

I'm slogging my way through the schematics for Mr Haible's FS-1A project, and something caught my eye. On Board 2, the outputs for U5B and U5C are tied together, and U6B and U6C are also tied together.

I had heard in the past that outputs should not be tied together like this without a mixer circuit (even a passive one), so what is going on here?
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PHOBoS



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PostPosted: Tue May 11, 2021 11:40 am    Post subject: Reply with quote  Mark this post and the followings unread

ehm scratch

The opamps will probably be fine but yeah, that's odd

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Blue Hell
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PostPosted: Tue May 11, 2021 1:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Looks like a drawing error to me .. is there a PCB design available to check it against?
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Steveg



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PostPosted: Thu May 13, 2021 4:02 am    Post subject: Reply with quote  Mark this post and the followings unread

It looks like the same design as this circuit https://www.researchgate.net/figure/Circuit-for-the-90-phase-shifter_fig4_228778023 which does not have the cross connectors. Given the design intent for the circuit it is hard to see how they would help.
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