Diodes for transients

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In this thread, https://www.electro-tech-online.com/threads/how-to-choose-opto-isolator.144973/#post-1224237 Crutschow posted a schematic showing a reversed diode used for reverse transient protection. Drawing below, D1 is the one in question.

My question is, would a TVS diode work in this circuit? I'm very new to designing circuits and trying to understand the how's and why's of what people are doing. Some other circuits I've seen use this too, but most don't.

I had two understandings about diodes. 1. they block reverse voltage and 2. they are destroyed by a high reverse voltage. Any help in this is appreciated.

 

[Tony Stewart]

U3 has PNP inputs with a single supply, so any negative voltage can potential forward bias the Vbc input junction instead of Vbe. The BC junction is much lower capacitance and higher resistance than the BE junction and will catastrophically fail when forward biased with any significant load. Thus the LM358 has an ABSOLUTE MAXIMUM input voltage of -0.3V. In case of load dump or short transient, the LM358 must be protected at all costs from not going below this voltage, so that the input differential pair can properly function and not become unpredictable below ground.

Thus I would use a Schottky diode for protection and not a Silicon diode for a lower threshold of 0.2V at low current.

TVS are special diodes that offer low capacitance but have a higher threshold voltage and are designed to switch in an avalanche mode for super fast transition times and extremely low ESR which can handle very large power transients. TVS come in varying thresholds starting above 5V so it would offer no protection for this LM358 input.

All CMOS logic has this kind of Schottky diode input ESD protection with diodes to actually both rails, but for different reasons to prevent SCR CMOS latchup.

 

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In Crutschows defense he mentioned in the text that a Schottky would be better for this.

Answering "tech speak" doesn't really help a novice like me. With the anode of the diode to ground/common what is it conducting? How is it conducting or what is it doing? Can't seem to find any reference to diodes used in this way, unless I'm using the wrong search term.