Ac analysis of common collector amplifier analysis

Transistor Circuit Design Tutorial Includes: Transistor circuit design Circuit configurations Common emitter Common emitter circuit design Emitter follower Common base See also: Transistor circuit types The common collector circuit configuration is more widely known as the emitter follower and it provides a high input impedance and a low output impedance. This means that the emitter follower circuit provides an ideal buffer stage, and as a result it is used in many circuits where there is a need not to load a circuit like an oscillator or other circuit, but provide a lower impedance to the following stages. The electronic circuit design for the emitter follower or common collector stage is very straightforward requiring just a few electronic components and some very simple calculations. The common collector transistor circuit configuration gains its name from the fact that the collector circuit is common to both input and output circuits, the base being associated with only the input, then the emitter with the output only. The other name for the common collector is emitter follower.

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• BJT as Common Collector Amplifier – Transistor in Common Collector Configuration
• Transistor Load Line Analysis
• BJT Common Collector Amplifier
• Common Collector Amplifier Electrical Engineering (EE) Notes | EduRev
• Electrical – DC and AC analysis of a Common Emitter Amplifier Circuit
• Designing and Measuring a Common-Collector Amplifier
• The Common-Collector Amplifier
• Common Collector Amplifier or the Emitter Follower
• The Common-Collector Amplifier Input and Output Resistance – The Proof

WATCH RELATED VIDEO: Common Collector Amplifier

BJT as Common Collector Amplifier – Transistor in Common Collector Configuration

The quiescent collector current I C , of a transistor is increased by changing resistances. As a result.

Answer: C. All capacitances are large. The overall Transconductance g m of the composite transistor is. Answer: D. All capacitors are very large.

The output impedance is. Which of the following statements are correct for biasing transistor amplifier configurations? CB amplifier has low input impedance and a low current gain. CC amplifier has low output impedance and a low current gain. CE amplifier has very poor voltage gain but has very high input impedance. The current gain of CB amplifier is higher than the current gain of CC amplifier.

Answer: A. Take the DC base emitter voltage drop as 0. Answer: Two non-inverting amplifiers, one having a unity gain and the other having a gain of 20 are made using identical operational amplifiers.

As compared to unity gain amplifier, the amplifier with gain 20 has. Less negative feedback. Greater negative feedback.

Less bandwidth. None of the above. Answer: B. A common emitter transistor amplifier has a collector current of 1. An RC coupled amplifier is assumed to have a single pole low frequency transfer function. Answer: Hz. Match the following:. Answer: a-2, b-3, c A common emitter amplifier with an external capacitors C C connected across the base and the collector of the transistor is shown.

Determine the upper cutoff frequency f H of the amplifier. Answer: a In the BJT amplifier shown in figure, the transistor is based in the forward active region. Putting a capacitor across R E will. Decrease the voltage gain and decrease the input impedance. Increase the voltage gain and decrease the input impedance. Increase the voltage gain and increase the input impedance. Evaluate small signal voltage gain A VS at a frequency of 10 kHz, and input resistance R i for two cases:.

The bypass capacitor C E is removed leaving R E unbypassed. Answer: a , 2. In the circuit shown, determine the resistance R o seen by the output terminals. Ignore the effect of R 1 and R 2. An amplifier is assumed to have a single pole high frequency transfer function. The rise time of its output response to a step function input is 35 nsec.

The upper -3 dB frequency in MHz for the amplifier to a sinusoidal input is approximately at. A bipolar junction transistor amplifier is shown below. Introducing a resistor in the emitter of a CE amplifier stabilizes the dc operating point against variations in. Only the temperature. What is the approximate voltage gain if C e is removed? What will be the output Vo, if C b is short circuited?

Below figure shown is a common base amplifier. Write expressions for the time constants associated with the capacitances C b and C s. What is the approximate lower cutoff frequency of the amplifier?

The current gain of a BJT is. An emitter follower amplifier is shown below, where Z i is the impedance looking into the base of the transistor and Z o is the impedance looking into the emitter of the transistor. Draw the small signal equivalent circuit of the amplifier. Obtain an expression for Z i. Obtain an expression for Z o. Determine Z i and Z o , if a capacitor C is connected across R 1.

Choose the correct match of input resistance of various amplifier configurations shown below:. Configuration Input resistance. A bipolar transistor is operating in the active region with a collector current of 1 mA. Common Data for Questions 1, 2 and 3 :. The capacitance C C can be assumed to be infinite. Under the DC conditions, the collector to emitter voltage drop is.

Statement for Linked Answer Question:. The value of DC current I E is. The mid-band voltage gain of the amplifier is approximately. Which expression best approximate V o t. The amplifier circuit shown below uses a silicon transistor. The capacitors C C and C E can be assumed to be short at signal frequency and effect of output resistance r o can be ignored. The input resistance R i increases and magnitude of voltage gain A V decreases.

The input resistance R i decreases and magnitude of voltage gain A V increases. The input resistance R i decreases and magnitude of voltage gain A V decreases. The input resistance R i increases and magnitude of voltage gain A V increases. Common Data Questions:. Consider the common emitter amplifier shown below with the following circuit parameters. The resistance seen by the source V S is. The lower cutoff frequency due to C 2 is.

In the circuit shown below, capacitors C 1 and C 2 are very large and are shorts at the input frequency. The voltage gain A v , of the circuit shown below is. A BJT is biased in forward active mode. If the emitter resistance in a common emitter voltage amplifier is not bypassed, it will.

Reduce both the voltage gain and the input impedance. Reduce the voltage gain and increase the input impedance. Increase the voltage gain and reduce the input impedance. Increase both the voltage gain and the input impedance. Answer: 0. Consider the common collector amplifier in the figure bias circuitry ensures that the transistor operates in forward active region, but has been omitted for simplicity.

Also, g m and r o are the small signal Transconductance and output resistance of the transistor, respectively. Which one of the following conditions ensures a nearly constant small signal voltage gain for a wide range of values of R E? Consider the bode plot shown in figure. Assume that all the poles and zeros are real valued. Anonymous April 30, at PM. Unknown September 16, at PM.

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Transistor Load Line Analysis

Consider the common-collector amplifier in the figure bias circuitry ensures that the transistor operates in forward active region, but has been omitted for simplicity. Which one of the following conditions ensures a nearly constant small-signal voltage gain for a wide range of values of R E? Start Learning. This question was previously asked in. Attempt Online.

BJT Common Collector Amplifier

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Common Collector Amplifier Electrical Engineering (EE) Notes | EduRev

The schematic diagram of a common-collector amplifier configuration is shown below. It is called the common-collector configuration because ignoring the power supply battery both the signal source and the load share the collector lead as a common connection point as in Figure below. It should be apparent that the load resistor in the common-collector amplifier circuit receives both the base and collector currents, being placed in series with the emitter. Since the emitter lead of a transistor is the one handling the most current the sum of base and collector currents, since base and collector currents always mesh together to form the emitter current , it would be reasonable to presume that this amplifier will have a very large current gain.

Electrical – DC and AC analysis of a Common Emitter Amplifier Circuit

The quiescent collector current I C , of a transistor is increased by changing resistances. As a result. Answer: C. All capacitances are large. The overall Transconductance g m of the composite transistor is. Answer: D.

Designing and Measuring a Common-Collector Amplifier

This article deals with another type of bipolar transistor architecture used to amplify signals that is commonly known as Common Collector Amplifier CCA. The CCA can also sometimes be called emitter-follower amplifier and we will understand why later in this article. The first figure below is a simplified electric diagram with no particular biasing circuit presenting the CCA configuration :. We see in Figure 2 an equivalent circuit of the CCA configuration of Figure 1 considering the transistor such as described above. It is easy to understand that in the configuration presented in Figure 1 , the voltage gain is approximately equal to 1. To provide better stability, the base of the bipolar transistor is biased with a voltage divider network such as shown in the following figure. V out. Thus, the bias resistances R 1 and R 2 should approximately be equal.

The Common-Collector Amplifier

The circuit uses voltage divider bias to derive the transistor base voltage V B from the supply. The transistor collector terminal is directly connected to V CC, no collector resistor is used. The circuit output voltage is developed across the emitter resistor R E , and there is no bypass capacitor. When a signal is applied via C 1 to the transistor base, V B increases and decreases as the signal goes positive and negative.

Common Collector Amplifier or the Emitter Follower

RELATED VIDEO: Common Collector amplifier analysis Electronics 2

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The Common-Collector Amplifier Input and Output Resistance – The Proof

The Application Activity in this section involves a preamplifier circuit for a public address system. The complete system includes the preamplifier, a power amplifier, and a dc power supply. You will focus on the preamplifier in this section and then on the power amplifier in Section 7. The things you learned about biasing a transistor in Section 5 are now applied in this section where bipolar junction transistor BJT circuits are used as small-signal amplifiers. The term small-signal refers to the use of signals that take up a relatively small percentage of an amplifier's operational range. Additionally, you will learn how to reduce an amplifier to an equivalent dc and ac circuit for easier analysis, and you will learn about multistage amplifiers. The differential amplifier is also covered.

In this article I will show a method to deduce the input and output resistance of the common collector amplifier. The common-collector amplifier is a well known circuit see Figure 1. It is mostly used as a buffer due to its high input resistance, small output resistance and unity gain. The equations derived in this article are symbolic, as is the derivation of any other formula in this website.