Table of Contents
- 1 What is the purpose of the emitter resistor in a BJT configuration?
- 2 What is the purpose of an emitter resistor?
- 3 Why do we use Re and Ce in a BJT amplifier?
- 4 What is the advantage of using emitter resistance in the context of biasing?
- 5 How do you choose a base resistor for a transistor?
- 6 What is the purpose of the base drive resistors R2 and R3 in the circuit?
- 7 Why common base configuration is seldom used?
What is the purpose of the emitter resistor in a BJT configuration?
As others have said, we use the emitter resistor to make bias points less sensitive to gain (hFE) variations. This is most commonly done for transistors biased in the active (linear) region, but can also be used for setting up operation in (or near) saturation or cut-off.
What is the purpose of an emitter resistor?
The aim of an AC signal amplifier circuit is to stabilise the DC biased input voltage to the amplifier and thus only amplify the required AC signal. This stabilisation is achieved by the use of an Emitter Resistance which provides the required amount of automatic biasing needed for a common emitter amplifier.
What is the role of emitter resistance in the transistor amplifier circuit?
What is the role of emitter resistance in the transistor amplifying circuit? The emitter resistor decreases effective input voltage decrease when collector current increases and thus it reduces collector current itself.
Why do we use Re and Ce in a BJT amplifier?
An Emitter bypass capacitor CE is used parallel with RE to provide a low reactance path to the amplified AC signal. If it is not used, then the amplified AC signal following through RE will cause a voltage drop across it, thereby dropping the output voltage.
What is the advantage of using emitter resistance in the context of biasing?
The main, most basic advantage is that emitter resistance reduces much of the circuit gain variability that otherwise is highly dependent on actual transistor current gain. The downside to this gain stability is that the emitter resistor causes a reduction in circuit gain.
Why common emitter transistor is mostly used?
Common emitter transistors are used most widely, because a common emitter transistor amplifier provides high current gain, high voltage gain and high power gain. This type of transistor gives for a small change in input there is small change in output.
How do you choose a base resistor for a transistor?
To calculate the base resistor, subtract the B-E 0.7V from the driver voltage and divide by the base current: 4.5-0.7 = 3.8V / 400uA = ~9.5K ohms max. The difference in CE drop between a factor of ten and using the beta is neglible for relatively slow on/off circuits, and it lowers the driver current requirement.
What is the purpose of the base drive resistors R2 and R3 in the circuit?
The resistances of R1, R2, R3, and Rfeedback function together as a signal-mixing network so that the voltage seen at the base of the transistor (with respect to ground) is a weighted average of the input voltage and the feedback voltage, resulting in a signal of reduced amplitude going into the transistor.
What are the merits of base resistor biasing method?
Advantages
- The circuit is simple.
- Only one resistor RE is required.
- Biasing conditions are set easily.
- No loading effect as no resistor is present at base-emitter junction.
Why common base configuration is seldom used?
The common base configuration is less common as an amplifier than compared to the more popular common emitter, (CE) or common collector, (CC) configurations but is still used due to its unique input/output characteristics.