(ii) When R B is made equal to 50 kΩ, then it is easy to see that base current is doubled i.e. (i) Referring to Fig.2 (ii) and applying Kirchhoff ’s voltage law to the circuit ABEN, we get, It may be noted that negative terminals of the power supplies are grounded to get a complete path of current. Here, we need show only the supply voltages, + 2V and +9V. The same circuit is shown in a simplified way in Fig. 2 (i), biasing is provided by a battery V BB (= 2V) in the base circuit which is separate from the battery V CC (= 9V) used in the output circuit. (ii) If R B in this circuit is changed to 50 kΩ, find the new operating point. (i) Determine the collector current I C and collector-emitter voltage V CE .
2 (i) shows biasing with base resistor method. ∴ Base voltage (signal voltage) = Collector current / (5 mA/V )= 3 mA /( 5 mA/V) = 600 mV Q3. Fig.
Now Collector current / Base voltage (signal voltage) = 5 mA/V allowed collector current, i C =12 V /R C = 12 V/ 4 KΩ = 3 mA allowed voltage across R C = 13 − 1 = 12 V What is the maximum input signal if β = 100 ? Given V knee = 1V and a change of 1V in V BE causes a change of 5mA in collector current. Due to VCB, the junction at the base-emitter gets forward-biased.During the positive peak of the signal, i C = 1 + 1 = 2mAĪnd during the negative peak (point B), i C = 1 − 1 = 0 mA Q2. A transistor employs a 4 kΩ load and V CC = 13V. The value of the zero signal of the current at the base can be determined by the voltage applied at the junction in between the terminals collector and base (VCB) instead of VCC. This method has a resistor at the base such that one end of it is connected to the terminal base whereas the other end will be connected to the collector. Transistor Biasing with Collector-Feedback Resistor The negative path of feedback followed makes the voltage gain smaller.If the RL gets short-circuited the value of stability becomes large.The change of Q-point is less when compared to the base bias method.This results in an increase in the value of the voltage at the collector-emitter terminal and the current at the base get reduced. If the current at the collector tends to increase the voltage at the load resistor gets increased. This indicates that voltage is shared among the base and collector terminals. Hence to obtain an intended outcome biasing plays a major role.įrom VCC, the current supplied flows through RL then it reaches the resistor present at the base. If the transistor is not biased appropriately, it may lead to the poor amplification of the signals resulting in the gain being very low. This type of technique is known as transistor biasing. To achieve the desired switching or the amplification effect a transistor must be supplied with the control amounts of voltages and currents through it. To enter into various modes of operation transistor biasing is done. Transistors are designed to operate in various modes among which active mode is preferred for amplification. The establishment of the operating points will be based on the selection of bias and load resistors.
To make the transistor function convincingly it must possess certain conditions to operate.
The transistors are one of the most frequently used semiconductors utilized in the applications of switching and amplification. But the complexity of designing vacuum tubes, more amount of power consumption paved the way for the inception of transistors in modern electronics. Before the use of transistors, vacuum tubes used for the purpose to control electronic signals. Transistors are developed in the year 1947 by the physicists of America named John Bardeen.
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