I'm studying Clipper Circuits on Diodes and connecting them to ground for the purpose of clipping off part of a input signal. During the positive alternation while the diode is forward bias they say that since the Cathode is at ground potential(0V), the Anode cannot exceed (.7 Volts). Then they go on to say that the output is clipped at +.7 Volts when the input exceeds this value.

My question is why exactly is the clipping taken place? They say the Anode cannot exceed .7 Volts because of the ground, but how can there even be any voltage at all (.7V while clippling anything higher) when the Anode is at Zero Volts Potential/Ground.

I know that you need to over-come the .7 Volts of a diodes potential barrier before current begins to flow, so I was expecting the output to be nothing. But to my suprise there is +.7 Volts during the positive alternation.

Can someone please help/explain? All help is appreciated...

 

The clipping is taking place because the diode conducts above 0.7V. Thus, the current is drawn by the diode so the output won't exceed 0.7V. Remember that when in full conduction, the diode has a dropout voltage of 0.7V. That is the voltage across the diode, identical to the output voltage. Think of it as a simple zener regulator.

Keep in mind that, in a typical clipping circuit, you have a resistor placed in series before the diode.

 

first realize that there are volt/amp characteristic curves for diodes, and when .6 to .7 volts forward bias is reached the current grows sharply. if the cathode is grounded, the anode is not at ground potential. it will be between 0 and .7 volts, depending on the input signal. upon reaching .7 volts, it essentially becomes a very conductive device and shorts everything above .7 volts through itself to ground.

 

Thank you Cumesoftware and Techroomt for your responses. So basically all the power that's being clipped off is going back through the diode to ground once the doide's barrier is overcome and it becomes conductive.

I understand now, I really appreciate it...

Slimm,