Here I have the image of a signal in the output of U2, and the output is shown in green in the graph(sorry for the poor quality). Highest value = 3.3V, Lowest value = 0V, sine wave, 60 Hz.
Now I have the same circuit but with that 1N4728 zener connected across and the output signal behaves like below:
The zener is working under low current(about 24mA) as its main Izt is Izt= 76mA, so I expected to have a voltage less than 3v3 as spice has shown.
Yet, the real question is I don't get the fact the zener is being able to clamp the output voltage without a resistor in series with it. In my understanding the zener should face the whole sinusoidal wave since there's no resistor in series to share the remaining voltage with. I tried that on real circuits with TL082 OpAmp and the same happened. I've also checked the TL082 output resistance and it's about 0.01 Ohm in the 60Hz range(which is the frequency of my signal), so that would for sure not be the trouble.
So, what exactly is going on in this circuit? Shouldn't a zener have a series resistor in order to clamp correctly?
Thank you for any help.