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I have done a simple electronic circuit with a bridge rectifier diode and I have observed an issue when I display the output signal. The output signal on some harmonic doesn't reach the 0 point as shown in the capture screen of my oscilloscope. Can any one explain the root cause of this issue? I have used the DF08 bridge rectifier.

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  • \$\begingroup\$ Is your source a signal generator? The secondary of a transformer? \$\endgroup\$ – vangelo Jun 28 at 14:30
  • \$\begingroup\$ Can you show the waveform of the input voltage? \$\endgroup\$ – Blue_Electronx Jun 28 at 14:41
  • \$\begingroup\$ Is your bridge rectifier was loaded during measurements? \$\endgroup\$ – G36 Jun 28 at 14:46
  • \$\begingroup\$ If the scope probe ground and your function generator (-) terminal are both connected to earth ground, you could see some funky results (though I'm not sure if you'd see what you're seeing...). Turn off the function generator and check the resistance between V1 (-) and Ch1 (-) using a multimeter to see if they are shorted through earth ground. \$\endgroup\$ – newothegreat Jun 28 at 14:55
  • \$\begingroup\$ The answer is due to diode impedance when Off , cause than probe capacitance or impedance on one side (+) to store voltage while I assume (-) is low impedance gnd. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 28 at 17:09
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This is generally caused by capacitance in the load and/or measuring device, or stray capacitance somewhere in the circuit. A high resistance load may not be able to discharge this capacitance fast enough to drop the voltage to zero during the zero crossing period.

In your case the effect is only occurring on every second half-cycle. This indicates an imbalance in the rectifier circuit, and suggests stray capacitance between the generator and ground may be the culprit.

I simulated your circuit in LTspice, first with the generator fully isolated and then with 15nF between its local ground and circuit ground.

The circuit:-

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Without stray capacitance:-

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With stray capacitance:-

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