MarkT:
GingerGiant:
MarkT:
IC1, the one on the right has no feedback network and there is no DC bias to pin 3 (non-inverting input). Both of those are
show-stoppers.That's actually part of the design. I was looking up op amps on wikipedia when I stumbled across the zero level detector.
Where's the link to this zero-level detector? It looks suspect to me - certainly the lack of DC bias to the input is a no-no.
No, it's fine as grounding the pin two (it's - input) sets it's operating point. Any positive voltage to the + input pin (even just a few millivolts) will cause the open loop amp to saturate to full positive output and any negative voltage (again just millivolts needed) will switch to full negative voltage output. An op-amp working as a simple comparator is operating as a logic switching device not as a linear amplifier.
http://4.bp.blogspot.com/-LTsyaMaEpz4/UB4u0NZfhUI/AAAAAAAABWo/Jn7U8xDBkJ0/s320/Circuit%2Bdiagram%2Bzero%2Bcrossing%2Bdetector-744414.jpgThe 741 isn't used very much these days, it walks with a zimmer-frame compared to modern op-amps!
Agreed, but the OP said he also has available 071 op-amps and while still pretty old they are heads and shoulders better then a 741.
Lefty
