Characteristics of BJT- CB Configuration
AIM:
To study the input output characteristics of Bipolar Junction Transistor in Common Emitter Configuration.
APPARATUS REQUIRED:
S.No | Components | Specification | quantity |
1 | Transistor | BC-107 | 1 |
2 | Resistor | 1kohm | 1 |
3 | Ammeter | (0-30)mA | 1 |
4 | Voltmeter | (0-30)V | 1 |
5 | Bread Board | 1 | |
5 | Regulated Power Supply | 0-30v | 1 |
THEORY:
Bipolar transistors are three-terminal devices that act as electrically controlled switches or as amplifier controls. These devices come in either npn or pnp configurations. An npn bipolar transistor uses a small input current and positive voltage at its base (relative to its emitter) to control a much larger collector-to-emitter current. Conversely, a pnp transistor uses a small output base current and negative base voltage (relative its emitter) to control a larger emitter-to-collector current.
Bipolar transistors are incredibly useful devices. Their ability to control current flow by means of applied control signals makes them essential elements in electrically controlled switching circuits, current-regulator circuits, voltage-regulator circuits, amplifier circuits, oscillator circuits, and memory circuits.
PROCEDURE:
INPUT CHARACTERISTICS
1. Connect the circuit as per the circuit diagram.
2. Set VCB=5V and vary VEB in steps.
3. Note down the corresponding IE values.
4. Repeat the same procedure for different values of VCB.
5. Plot the graph VEB against IE for constant VCB.
OUTPUT CHARACTERISTICS
1. Connect the circuit as per the circuit diagram.
2. Set IE=2mA and vary VCB in steps.
3. Note down the corresponding IC.
4. Repeat the same procedure for different values of IE.
5. Plot the graph VCB against IC for constant IE.
RESULT:
Thus the input and output characteristics of a Bipolar Transistor in Common Base Configuration is thus studied.
Characteristics of JFET-CS Configuration
AIM:
To study the Drain Characteristics and Transfer Characteristics of JFET in Common Source Configuration.
APPARATUS REQUIRED:
S.No | Components | Specification | quantity |
1 | Transistor | BC-107 | 1 |
2 | Resistor | 1kohm | 1 |
3 | Ammeter | (0-30)mA | 1 |
4 | Voltmeter | (0-30)V | 1 |
5 | Bread Board | 1 | |
6 | Regulated Power Supply | 0-30v | 1 |
THEORY:
The field-effect transistor (FET) is an active “voltage” device. Unlike bipolar transistors, FETs are not current amplifiers. Rather, they act much like vacuum tubes in basic operation. FETs are three-lead devices similar in appearance to bipolar transistors. The three leads are referred to as the gate, source, and drain. These three leads are somewhat analogous to the bipolar transistor’s base, emitter, and collector leads, respectively. There are two general types of FETs: junction field-effect transistors (JFETs) and insulated-gate metal oxide semiconductor field-effect transistors (MOSFET or IGFET).
FETs are manufactured as either N-channel or P-channel devices. N-channel FETs are used in applications requiring the drain to be positive relative to the source; the opposite is true of P-channel FETs. Note that the arrow always points toward the channel (the interconnection between the source and drain) when symbolizing N-channel FETs, and away from it in P-channel symbologies. All types of FETs have very high input impedances (1 Mohm to over 1,000,000 Mohm). This is the primary advantage to using FETs in the majority of applications. The complete independence of FET operation from its input current is the reason for their classification as voltage devices. Because FETs do not need gate current to function, they do not
have an appreciable loading effect on preceding stages or transducers. Also, because their operation does not depend on “junction recombination” of majority carriers (as do bipolar transistors), they are inherently low-noise devices.
PROCEDURE:
DRAIN CHARACTERISTICS
1. Connect the circuit as the circuit diagram.
2. Set the gate voltage VGS=-1V.
3. Vary the drain voltage VDS in steps.
4. Note down the corresponding drain current ID.
5. Repeat the same procedure for different values of VGS.
6. Plot the graph VDS against ID for a constant VGS.
TRANSFER CHARACTERISTICS
1. Connect the circuit as the circuit diagram.
2. Set the gate voltage VDS=5V.
3. Vary the gate voltage VGS in steps.
4. Note down the corresponding drain current ID.
5. Repeat the same procedure for different values of VDS.
6. Plot the graph VGS against ID for a constant VDS.
RESULT:
Thus the drain characteristics and transfer characteristics of JFET is studied.
Characteristics of Enhancement MOSFET
AIM:
To study the V-I characteristics of MOSFET in Enhancement mode.
APPARATUS REQUIRED:
S.No | Components | Specification | quantity |
1 | Transistor | BFW11 | 1 |
2 | Resistor | 1kohm | 1 |
3 | Resistor | 100 ohm | 1 |
3 | Ammeter | (0-30)mA | 1 |
4 | Voltmeter | (0-30)V | 1 |
5 | Bread Board | 1 | |
6 | Regulated Power Supply | 0-30V | 1 |
THEORY:
In an n-channel MOSFET, the gate (positive plate), metal oxide film (dielectric), and substrate (negative plate) form a capacitor, the electric field of which controls channel resistance. When the positive potential of the gate reaches a threshold voltage VT (typically 2 to 4V), sufficient free electrons are attracted to the region immediately beside the metal oxide film (this is called enhancement-mode operation) to induce a conducting channel of low resistivity. If the source-to-drain voltage is increased, the enhanced channel is depleted of free charge carriers in the area near the drain, and pinchoff occurs as in the JFET.
Although the enhancement-mode MOSFET is the more popular (it is widely used in digital switching circuits), a depletion-mode MOSFET, characterized by a lightly doped channel between heavily doped source and drain electrode areas, is commercially available that can be operated like the JFET. However, that device displays a gate-source input impedance several orders of magnitude smaller than that of the JFET. However, that device displays a gate-source input impedance several orders of magnitude smaller than that of the JFET.
PROCEDURE:
1. Connect the circuit as the circuit diagram.
2. Set the gate voltage VGS=-1V.
3. Vary the drain voltage VDS in steps.
4. Note down the corresponding drain current ID.
5. Repeat the same procedure for different values of VGS.
6. Plot the graph VDS against ID for a constant VGS.
Characteristics of SCR
AIM:
To study the characteristics of SCR and to find the Latching and Holding Current.
APPARATUS REQUIRED:
S.No | Components | Specification | quantity |
1 | SCR | 1 | |
2 | Resistor | 1kohm | 1 |
3 | Ammeter | (0-30)mA | 2 |
4 | Voltmeter | (0-30)V | 1 |
5 | Bread Board | 1 | |
6 | Regulated Power Supply | 0-30V | 1 |
THEORY:
SCRs are three-lead semiconductor devices that act as electrically controlled switches. When a specific positive trigger voltage/current is applied to the SCR’s gate lead (G), a conductive channel forms between the anode (A) and the cathode (C) leads. Current flows in only one direction through the SCR, from anode to cathode (like a diode). Another unique feature of an SCR, besides its current-controlled switching, has to do with its conduction state after the gate current is removed. After an SCR is triggered into conduction, removing the gate current has no effect. That is, the SCR will remain on even when the gate current/voltage is removed. The only way to turn the device off is to remove the anode-to-cathode current or to reverse the anode and cathodes polarities.
In terms of applications, SCRs are used in switching circuits, phase-control circuits, inverting circuits, clipper circuits, and relay-control circuits, to name a few.
PROCEDURE:
1. Connect the circuit as per the circuit diagram.
2. Set the gate current equal to the fixing current.
3. Vary Anode to Cathode Voltage VAK in steps of 0.5V.
4. Note down the corresponding Anode current IA.
5. VBO is the voltage VAK suddenly drops and there is a sudden increase in anode current IA.
6. Note that the current at this point of VBO. This is called the latching current.
7. Increase the voltage VAK in steps of 1V.
8. Now open the gate terminal and decrease VAK.
9. Note the holding current. It is the current below which the deflection in voltmeter and ammeter reduces to zero suddenly.
10. Now reverse the voltage applied to the SCR.
11. It function just the reverse biased PN junction diode.
12. Plot the graph VAK against IA.
13. Note the forward blocking region.
RESULT:
Thus the characteristics of SCR is studied and the break over voltage is noted.
Thus the characteristics of SCR is studied and the break over voltage is noted.
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