# 42 Lecture

## Collector Emitter Loop

The Collector Emitter Loop, or C-E Loop, is a fundamental concept in Bipolar Junction Transistor (BJT) circuits.

## Important Mcq's Midterm & Finalterm Prepration Past papers included

What is the voltage drop across the collector-emitter junction in a BJT when it is operating in the active region?

a. approximately zero

b. approximately 0.2 volts

c. approximately 0.6 volts

d. approximately the same as the supply voltage

In a common emitter BJT configuration, which of the following currents flow in the collector-emitter loop?

a. only the collector current

b. only the base current

c. only the emitter current

d. both the collector and emitter currents

Answer: d. both the collector and emitter currents

What is the purpose of the collector resistor in a BJT circuit?

a. to limit the base current

b. to provide negative feedback

c. to stabilize the bias point

d. to provide a load for the transistor

What is the typical value of the collector current in a BJT operating in the active region?

a. microamps

b. milliamps

c. amps

d. tens of amps

Which of the following is true about the direction of the collector current in a PNP transistor?

a. it flows from the emitter to the collector

b. it flows from the collector to the emitter

c. it flows in both directions

d. it does not flow in a PNP transistor

Answer: a. it flows from the emitter to the collector

What is the direction of the voltage drop across the collector-emitter junction in a BJT operating in the active region?

a. positive on the collector and negative on the emitter

b. negative on the collector and positive on the emitter

c. positive on both the collector and emitter

d. negative on both the collector and emitter

Answer: b. negative on the collector and positive on the emitter

Which of the following is true about the direction of the base current in a BJT?

a. it flows from the emitter to the collector

b. it flows from the collector to the emitter

c. it flows in both directions

d. it does not flow in a BJT

Answer: b. it flows from the collector to the emitter

In a common base BJT configuration, which of the following currents flow in the collector-emitter loop?

a. only the collector current

b. only the base current

c. only the emitter current

d. both the collector and emitter currents

Answer: a. only the collector current

What is the typical value of the voltage drop across the base-emitter junction in a BJT operating in the active region?

a. approximately zero

b. approximately 0.2 volts

c. approximately 0.6 volts

d. approximately the same as the supply voltage

Which of the following is true about the direction of the emitter current in a BJT?

a. it flows from the emitter to the collector

b. it flows from the collector to the emitter

c. it flows in both directions

d. it does not flow in a BJT

Answer: a. it flows from the emitter to the collector

## Subjective Short Notes Midterm & Finalterm Prepration Past papers included

What is the collector-emitter loop?

The collector-emitter loop is the path that current takes through the collector and emitter terminals of a bipolar junction transistor (BJT) when the transistor is in active mode.

What is the significance of the collector-emitter loop?

The collector-emitter loop is significant because it determines the voltage gain and current gain of a BJT. It also determines the maximum power that can be dissipated by the transistor without causing damage.

What is the role of the collector-emitter loop in amplification?

The collector-emitter loop plays a critical role in amplification because it allows for small changes in the base current to produce large changes in the collector current. This allows the BJT to act as an amplifier.

What is the effect of increasing the collector resistance on the collector-emitter loop?

Increasing the collector resistance will decrease the slope of the collector-emitter loop, which will reduce the voltage gain of the BJT.

What happens if the collector-emitter loop is opened?

If the collector-emitter loop is opened, the BJT will not function as an amplifier because no current can flow through the transistor.

What is the effect of increasing the base current on the collector-emitter loop?

Increasing the base current will cause the collector current to increase, which will cause the collector-emitter loop to shift upward.

How does temperature affect the collector-emitter loop?

Temperature can affect the collector-emitter loop by changing the characteristics of the transistor. For example, an increase in temperature can cause the saturation current to increase, which will cause the collector-emitter loop to shift downward.

What is the significance of the slope of the collector-emitter loop?

The slope of the collector-emitter loop determines the voltage gain of the BJT. A steeper slope results in a higher voltage gain.

What is the effect of increasing the load resistance on the collector-emitter loop?

Increasing the load resistance will cause the collector-emitter loop to shift downward, which will reduce the voltage gain of the BJT.

How does the collector-emitter loop affect the stability of the BJT?

The stability of the BJT is affected by the shape and position of the collector-emitter loop. If the loop is unstable, the BJT may oscillate, which can cause distortion or even damage to the transistor.

Collector-Emitter Loop The Collector Emitter Loop, or C-E Loop, is a fundamental concept in Bipolar Junction Transistor (BJT) circuits. The loop consists of the collector, emitter, and base terminals of the BJT, and it forms a closed circuit for the flow of current in the device. When a voltage is applied to the base terminal of a BJT, the resulting current flow through the base-emitter junction causes a corresponding current flow in the collector-emitter junction. This effect is amplified by the transistor, resulting in a larger collector current than the base current. The collector-emitter loop can be analyzed using Kirchhoff's Voltage Law (KVL), which states that the sum of the voltages around a closed loop is zero. In the C-E loop, the voltage drop across the collector-emitter junction, V_CE, is equal to the sum of the voltage drop across the base-emitter junction, V_BE, and the voltage drop across the load resistor, R_L. V_CE = V_BE + V_RL The current in the loop is determined by Ohm's Law, which states that the current flowing through a resistor is directly proportional to the voltage across it and inversely proportional to its resistance. I_C = (V_CC - V_CE) / R_L Where I_C is the collector current, V_CC is the supply voltage, and R_L is the load resistor. By manipulating these equations, we can determine the characteristics of the BJT circuit. For example, we can calculate the saturation voltage, which is the voltage at which the collector-emitter junction is fully forward-biased and the transistor is fully turned on. V_CE(sat) = V_BE(on) + V_RL Where V_BE(on) is the base-emitter junction voltage when the transistor is on. Another important characteristic is the gain of the transistor, which is the ratio of the change in collector current to the change in base current. ? = ?I_C / ?I_B The gain can be influenced by factors such as temperature and voltage, and it is an important parameter for designing BJT circuits. In summary, the C-E loop is a key concept in BJT circuits, and it can be analyzed using KVL and Ohm's Law to determine the characteristics of the circuit. Understanding the behavior of the loop is essential for designing and analyzing BJT circuits, and it is a fundamental part of circuit theory.