Which of the following is method to model a diode’s forward characteristics?
All of the mentioned are different methods used to model a diode’s forward characteristics.
A voltage regulator needs to provide a constant voltage in spite of the fact that there may be
Voltage regulators are required in both of the situations mentioned.
For the circuit shown below calculate
Calculate the %age change in the regulated voltage caused by a change of ±10% in the input voltage. (RL is not connected to the circuit)
Current I in the circuit = (10 – 2.1) / 1 or 7.9 mA
Incremental resistance of each diode is rd = 25mV/7.9mA at room temperature or 3.2Ω
Total resistance of the diode connection = r = 9.6Ω
The series combination of R and r acts as a voltage divider, hence
▲V0 = ±r/r+R or 9.5 mA or ± 0.5%.
Calculate the change in the voltage when RL is connected as shown
When RL is connected it draws approx. 2.1v/1000 A current or 2.1 mA. Hence the current in the diode decreases by approximately 2.1 mA. The voltage change across the diode is thus -2.1mA * 9.6 Ω or -20mA.
The value of the diode small-signal resistance rd at bias currents of 0.1 mA is
Thermal voltage at room temperature is 25mV and the current is 0.1mA. rd = 25mV/0.1mA or 250 Ω.
In many applications, a conducting diode is modeled as having a constant voltage drop, usually approximately
Normally a silicon diode has a voltage drop of 0.7V.
The graphical method of modeling a diode characteristics is based on
Graphical method uses equations obtained in the exponential method and then the Answer of these equations is obtained by plotting them on a graph.
For small-signal operation around the dc bias point, the diode is modeled by a resistance equal to the
It is a required characteristic for small-ground operations.
The other name for bias point is
Quiescent point is also called base point. It is due to this name that is also called Q–point.
In iteration method for modelling a diode the answer obtained by each subsequent iteration is
True value is obtained by the exponential method and therefore both of the statements are true.