AIM: To draw the V-I characteristics of a given Zener diode and to determine the reverse breakdown voltage forward knee voltage and Zener resistance.
APPARATUS: Zener diode, 1KW resistor, DC regulated power supply, voltmeter, milliammeter.
PRINCIPLE: A Zener diode is essentially a heavily doped p-n junction diode. Its symbol is shown in figure (1).
When the Zener diode is forward biased, the forward current increases with the increase in applied voltage. When it is reverse biased, a small reverse current flows until the breakdown voltage is reached. In the vicinity of breakdown region, the reverse current starts rising rapidly because of avalanche effect. Finally a sharp increase in current occurs when the Zener breakdown voltage (Vz) is reached. In this region, a small voltage change results in a large current change. This voltage limiting characteristics of a Zener diode makes it a good voltage regulator.
PROCEDURE:
FORWARD CHARACTERISTICS:
Connections are made as shown in figure (2).
The voltage is varied gradually and the corresponding current values are noted down.
REVERSE CHARACTERISTICS:
Connections are made as shown in figure (3).
The voltage is varied gradually and the corresponding current values are noted down.
A graph can be plotted with the voltage along X-axis and the current along the Y-axis. During the forward bias, the voltage at which current increases sharply is called forward knee voltage (Vk). In the reverse bias graph, extrapolating straight line portion to the X-axis will yield Zener breakdown voltage. The slope on the linear part of the curve gives Zener resistance, Rz = DV/DI
APPARATUS: Zener diode, 1KW resistor, DC regulated power supply, voltmeter, milliammeter.
PRINCIPLE: A Zener diode is essentially a heavily doped p-n junction diode. Its symbol is shown in figure (1).
When the Zener diode is forward biased, the forward current increases with the increase in applied voltage. When it is reverse biased, a small reverse current flows until the breakdown voltage is reached. In the vicinity of breakdown region, the reverse current starts rising rapidly because of avalanche effect. Finally a sharp increase in current occurs when the Zener breakdown voltage (Vz) is reached. In this region, a small voltage change results in a large current change. This voltage limiting characteristics of a Zener diode makes it a good voltage regulator.
PROCEDURE:
FORWARD CHARACTERISTICS:
Connections are made as shown in figure (2).
The voltage is varied gradually and the corresponding current values are noted down.
REVERSE CHARACTERISTICS:
Connections are made as shown in figure (3).
The voltage is varied gradually and the corresponding current values are noted down.
A graph can be plotted with the voltage along X-axis and the current along the Y-axis. During the forward bias, the voltage at which current increases sharply is called forward knee voltage (Vk). In the reverse bias graph, extrapolating straight line portion to the X-axis will yield Zener breakdown voltage. The slope on the linear part of the curve gives Zener resistance, Rz = DV/DI
OBSERVATIONS:
FORWARD CHARACTERISTICS:
Voltage ( Volts) Current (mA)
REVERSE CHARACTERISTICS:
Voltage ( Volts) Current (mA)
FORWARD CHARACTERISTICS:
Voltage ( Volts) Current (mA)
REVERSE CHARACTERISTICS:
Voltage ( Volts) Current (mA)
CALCULATIONS:
From I-V characteristics graph,
From I-V characteristics graph,
DV =
DI =
\RZ = DV/DI =
RESULTS:
I-V characteristics of a Zener diode are drawn.
The forward knee voltage (Vk) = Volts.
The Zener breakdown voltage (Vz) = Volts.
The Zener resistance (Rz) = Ohms
DI =
\RZ = DV/DI =
RESULTS:
I-V characteristics of a Zener diode are drawn.
The forward knee voltage (Vk) = Volts.
The Zener breakdown voltage (Vz) = Volts.
The Zener resistance (Rz) = Ohms
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