Emitter follower is a case of negative current feedback circuit. This is mostly used as a last stage amplifier in signal generator circuits. The important features of Emitter Follower are − It has high input impedance. It has low output impedance.
What is the major application of emitter follower amplifier?
The emitter follower has the following principal applications : (i) To provide current amplification with no voltage gain. (ii) Impedance matching. (i) Current amplification without voltage gain.
Why cascode amplifier is used?
The cascode amplifier is used to enhance the performance of an analog circuit. The utilization of cascode is a common method which can be used in the applications of transistors as well as vacuum tubes.
Which is also known as emitter follower?
In electronics, a common collector amplifier (also known as an emitter follower) is one of three basic single-stage bipolar junction transistor (BJT) amplifier topologies, typically used as a voltage buffer.
What is the difference between CE and emitter follower circuit?
The main difference between the two will be where the output is taken. For the common emitter amplifier, we will take the output at the collector of the transistor. For the emitter follower, the output will be taken at the emitter of the transistor.
What is voltage buffer?
A voltage buffer, also known as a voltage follower, or a unity gain amplifier, is an amplifier with a gain of 1. … A voltage gain of 1 means that if the input voltage goes up by ΔV , then the output voltage is also designed to go up by the same ΔV .
What are the significant characteristics of emitter follower?
The emitter follower is a current amplifier that has no voltage gain. Its most important characteristic is that it has high input impedance and low output impedance. This makes it an ideal circuit for impedance matching.
What is the value of gain in emitter follower?
The emitter follower (Figure 5.11(a)) is a buffer stage with high input impedance, low output impedance, and a gain of approximately unity.
How do PNP transistor?
The PNP transistor is a type of transistor in which one n-type material is doped with two p-type materials. … When a small current flow through the base of the PNP transistor, it turns on. The current in a PNP transistor flows from the emitter to the collector.
What is the most important fact about the collector current?
What is the most important fact about the collector current? It is measured in milliampere. It equals the base current divided by the current gain.
What is the difference between Cascade and cascode?
The difference between cascade and cascode amplifiers is that in cascade amplifiers the transistors are connected in series. Whereas in cascode amplifier transistors are connected in parallel. … While in a cascode amplifier, the transistor is placed one above the other.
What is common emitter configuration?
In common emitter configuration, base is the input terminal, collector is the output terminal and emitter is the common terminal for both input and output. Thus, the emitter terminal of a transistor is common for both input and output and hence it is named as common emitter configuration. …
Why are voltage buffers used?
A voltage buffer amplifier is used to transfer a voltage from a first circuit, having a high output impedance level, to a second circuit with a low input impedance level.
Why is it called voltage follower?
Because of this behavior, the common-collector amplifier circuit is also known as the voltage-follower or emitter-follower amplifier, because the emitter load voltage follows the input so closely. … The output is the same peak-to-peak amplitude as the input.
Why unity gain buffer is used?
This is the reason unity gain buffers are used. They draw very little current, not disturbing the original circuit, and give the same voltage signal as output. They act as isolation buffers, isolating a circuit so that the power of a circuit is disturbed very little.
Why is it called common emitter?
It is also named common- emitter amplifier because the emitter of the transistor is common to both the input circuit and output circuit. … Since the emitter is connected to the ground, it is common to signals, input and output. The common- emitter circuit is the most widely used of junction, transistor amplifiers.
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 many types of negative feedback are there?
Negative feedback can be achieved via four different forms. They differ in how the input and output impedances are changed. We have basically two choices when it comes to connecting the input and output of the amplifier to the output and input of the feedback network.
What is AC voltage gain?
The output voltage (on the collector terminal of the transistor) will have an AC component that is an amplified version of the input signal, superimposed on a DC voltage. The ratio of the AC component of the output to the AC component of the input is called the “gain”. The gain is usually between 5 an 20.
What is BJT transistor?
A Bipolar Junction Transistor, or BJT, is a solid-state device in which the current flow between two terminals (the collector and the emitter) is controlled by the amount of current that flows through a third terminal (the base).
Why we use cascode current mirror?
In order to suppress the effect of channel length modulation, a cascode current mirror can be used. … In the circuit of basic current mirror and Vb is chosen such that Vx = Vy, then Iout closely tracks Iref.
Why cascode current mirrors are used?
Advantages: 1. Cascode current mirror eliminates the channel length modulation effect by keeping Vds1 = Vds2 constant in the ratio: Iout = (W/L) (1+λVds2 ) (W/L) (1+λVds1) 2. Improves output resistance.
What is cascade stage?
A cascade amplifier is a two-port network designed with amplifiers which are connected in series when every amplifier transmits its o/p to the second amplifiers input in a daisy chain. The problem in measuring the gain of the cascaded stage is the non-perfect coupling among two stages because of loading.