AIM: To draw the input and output characteristics of given N-P-N transistor in the Common Emitter configuration and hence to determine the input resistance, output resistance and current gain b.
APPARATUS: N-P-N transistor, Variable DC power supplies, Digital voltmeter, DC Microammeter, DC Milliammeter, 100 KW Resistor and 100W Resistor.
PRINCIPLE: Transistor is a three terminal, two junction semiconductor device. The three terminals are Emitter, Base and Collector. In an N-P-N transistor, a P-type semiconductor is sandwiched between two N-type materials. Here Emitter is heavily doped, the Base is lightly doped and the Collector is intermediately doped. Common Emitter configuration is most effective because of its high current gain, high voltage and power gain. In Common Emitter configuration, Emitter terminal is made common to both input and output circuits. Input junction (Base-Emitter) is forward biased and output junction (Collector-Emitter) is reverse biased so that the input junction is having low resistance (since it is forward biased) and output junction high resistance (since it is reverse biased).
Input characteristics of a transistor is a curve showing the variation of input (Base) current IB as a function of input (Base-Emitter) voltage VBE, when the output (Collector-Emitter) voltage VCE is kept constant.
Input resistance Ri = (DVBE/ DIB)
Output characteristics of a transistor is a curve showing variations of output current IC as a function of output voltage VCE, when the input current IB is kept constant.
Output resistance Ro = DVCE/DIC
Current gain b = DIC/DIB
PROCEDURE: The circuit connections are made as shown in figure.
APPARATUS: N-P-N transistor, Variable DC power supplies, Digital voltmeter, DC Microammeter, DC Milliammeter, 100 KW Resistor and 100W Resistor.
PRINCIPLE: Transistor is a three terminal, two junction semiconductor device. The three terminals are Emitter, Base and Collector. In an N-P-N transistor, a P-type semiconductor is sandwiched between two N-type materials. Here Emitter is heavily doped, the Base is lightly doped and the Collector is intermediately doped. Common Emitter configuration is most effective because of its high current gain, high voltage and power gain. In Common Emitter configuration, Emitter terminal is made common to both input and output circuits. Input junction (Base-Emitter) is forward biased and output junction (Collector-Emitter) is reverse biased so that the input junction is having low resistance (since it is forward biased) and output junction high resistance (since it is reverse biased).
Input characteristics of a transistor is a curve showing the variation of input (Base) current IB as a function of input (Base-Emitter) voltage VBE, when the output (Collector-Emitter) voltage VCE is kept constant.
Input resistance Ri = (DVBE/ DIB)
Output characteristics of a transistor is a curve showing variations of output current IC as a function of output voltage VCE, when the input current IB is kept constant.
Output resistance Ro = DVCE/DIC
Current gain b = DIC/DIB
PROCEDURE: The circuit connections are made as shown in figure.
(a) Input characteristics: Power supply VCC is switched on and VCE is adjusted to a desired value by varying VCC. Base-Emitter voltage (VBE) is varied and corresponding base current (IB) is noted down. The readings are plotted with VBE along X-axis and IB along Y-axis. Slope of the graph will input resistance.
(b) Output characteristics: By varying VBB, IB is adjusted to a desired value. Now VCE is is varied and corresponding value of IC is noted down. The readings are plotted with VCE along X-axis and IC along Y-axis. Another set of observation is taken for different IB value and the graph is plotted. Slope of the graph will give output resistance.
(c) Current gain: Keeping VCE constant, collector current IC is noted for different values of base current IB. The experiment is repeated for various constant values of VCE and readings are tabulated. A graph is drawn with IB along X-axis and IC along Y-axis. Slope of the graph will give current gain b.
(b) Output characteristics: By varying VBB, IB is adjusted to a desired value. Now VCE is is varied and corresponding value of IC is noted down. The readings are plotted with VCE along X-axis and IC along Y-axis. Another set of observation is taken for different IB value and the graph is plotted. Slope of the graph will give output resistance.
(c) Current gain: Keeping VCE constant, collector current IC is noted for different values of base current IB. The experiment is repeated for various constant values of VCE and readings are tabulated. A graph is drawn with IB along X-axis and IC along Y-axis. Slope of the graph will give current gain b.
OBERVATIONS:
(a) Input characteristics:
VCE =
VBE IB
(a) Input characteristics:
VCE =
VBE IB
(b) Output characteristics:
IB IB IB
VCE IC VCE IC VCE IC
IB IB IB
VCE IC VCE IC VCE IC
(c) Current gain:
VCE VCE VCE
IB IC IB IC IBIC
VCE VCE VCE
IB IC IB IC IBIC
CALCULATIONS:
(1) Slope of the DVBE - DIB graph (Input resistance Ri) = DVBE/ DIB =
(2) Slope of the DVCE - DIC graph (Output resistance Ro) = DVCE/ DIC =
(3) Slope of the DIB - DIC graph (Current gain b) = DIB/ DIC =
RESULTS:
(1) The input and output characteristics are drawn.
(2) Input resistance Ri =
(3) Output resistance Ro =
(4) Current gain b =
(1) Slope of the DVBE - DIB graph (Input resistance Ri) = DVBE/ DIB =
(2) Slope of the DVCE - DIC graph (Output resistance Ro) = DVCE/ DIC =
(3) Slope of the DIB - DIC graph (Current gain b) = DIB/ DIC =
RESULTS:
(1) The input and output characteristics are drawn.
(2) Input resistance Ri =
(3) Output resistance Ro =
(4) Current gain b =
1 comment:
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