Diode Equivalent Models
Diode Equivalent Models
Diode Equivalent Models
1. Ideal diode allows the flow of forward current for any value of forward bias voltage.
Hence, Ideal diode can be modeled as closed switch under forward bias condition. This is
shown in the figure.
2. Ideal diode allows zero current to flow under reverse biased condition. Hence it can be
modeled as open switch. This is indicated in the figure.
2. SIMPLIFIED DIODE MODEL
The piece-wise linear model, as the name suggests, is a model in which the characteristics of diode is approximated
by “piece-wise linear” line segments. Now consider the straight line in the piece-wise linear characteristics. This
straight line indicates constant slope. Slope in the V-I graph indicates resistance. So we add a resistor in the diode
model.
The value of resistance can be found from the graph. We can see from the graph that the diode current changes from 0
to 15 mA for a voltage change from 0.7 to 0.8 V.
Thus the average value of resistance is (0.8 V-0.7 V)/(15 mA - 0 mA) = 6.67 Ω. Thus the value of resistance in the
equivalent model is approximately 6.67 Ω. The figure given below shows piece-wise linear characteristics of diode
along with the its model.
3. PIECE-WISE LINEAR MODEL
The piece-wise linear model, as the name suggests, is a model in which the characteristics of
diode is approximated by “piece-wise linear” line segments. Now consider the straight line in the
piece-wise linear characteristics. This straight line indicates constant slope. Slope in the V-I
graph indicates resistance. So we add a resistor in the diode model. The value of resistance can
be found from the graph. We can see from the graph that the diode current changes from 0 to 15
mA for a voltage change from 0.7 to 0.8 V. Thus the average value of resistance is (0.8 V-0.7
V)/(15 mA - 0 mA) = 6.67 Ω. Thus the value of resistance in the equivalent model is
approximately 6.67 Ω. The figure given below shows piece-wise linear characteristics of diode
along with the its model.