Volume III - Semiconductors » Zener diodes - few corrections needed

Discussion in 'Feedback and Suggestions' started by chindu, Jun 3, 2008.

1. chindu Thread Starter New Member

Jun 3, 2008
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Hi,
In Volume III - Semiconductors » DIODES AND RECTIFIERS » Zener diodes, I found few corrections to be done.
For your reference the original text is given below in blue:
If we connect a diode and resistor in series with a DC voltage source so that the diode is forward-biased, the voltage drop across the diode will remain fairly constant over a wide range of power supply voltages as in Figure below (a).
According to the diode equation, the current through a forward-biased PN junction is proportional to e raised to the power of the forward voltage drop. Because this is an exponential function, current rises quite rapidly for modest increases in voltage drop. Another way of considering this is to say that voltage dropped across a forward-biased diode changes little for large variations in diode current. In the circuit shown above, diode current is limited by the voltage of the power supply, the series resistor, and the diode's voltage drop, which as we know doesn't vary much from 0.7 volts. If the power supply voltage were to be increased, the resistor's voltage drop would increase almost the same amount, and the diode's voltage drop just a little. Conversely, a decrease in power supply voltage would result in an almost equal decrease in resistor voltage drop, with just a little decrease in diode voltage drop. In a word, we could summarize this behavior by saying that the diode is regulating the voltage drop at approximately 0.7 volts.
Below are the corrected text highlighted in green:
If we connect a diode and resistor in series with a DC voltage source, the diode is forward-biased and the voltage which drops across the diode will remain fairly constant over a wide range of power supply voltages as in Figure below (a).

According to the diode equation sorry I couldnt find this equation, the current which passes through a forward-biased PN junction is proportional to e (state that e in parentheses) raised to the power of the forward voltage drop. This is an exponential function because current rises quite rapidly for modest increases in voltage drop. Another way of considering this could be, the voltage dropped across a forward-biased diode changes slightly for large variations in diode current. In the circuit shown above (there is no circuit above this paragraph), diode current is limited by the series resistor and its voltage drop, as we know which doesn't vary much from 0.7 volts. If the power supply voltage needs to be increased, the resistor's voltage drop also increases almost the same amount and the diode's voltage drop slightly changes a little. Conversely, a decrease in power supply voltage would result in an equal decrease in resistor voltage drop, and a slight decrease in diode voltage drop. To summarize this behavior in a word is that the diode is regulating the voltage drop at approximately 0.7 volts.

I have done it for first two paragraphs. If needed, I can proceed with the rest of the text. Kindly reply me back.

Thanks,
Chindu

2. Unregistered Guest

hi
If we connect a diode and resistor in series with a DC voltage source so that the diode is forward-biased, the voltage drop across the diode will remain fairly constant over a wide range of power supply voltages as in Figure below (a).