Why do transistors amplify

The term between the brackets is a constant which we're not interested in at the moment. Then again ignoring the constant factor. So the output voltage is 10 times the input voltage plus a constant bias. Looks like we can use the transistor for voltage amplification as well. The signal is being amplified. Depending on the design of the transistor amplifier the actual base current may or may not be part of the output current. Don't get hung up on a definition of amplification that requires every input electron to get larger and then pass to the output Amplifiy sound, and you're amplifying the energy-flow: the input watts of sound become larger output watts.

Note that an electrical transformer doesn't amplify. It can step up voltage, but it cant increase the watts. Transistors and any sort of valve or switch can amplify. They do it by using a tiny wattage to control a power supply which can output a huge wattage. The large output comes from the power supply, while the input signal is valving the transistpr on and off.

If you have a giant hydraulic press, you can crush cars by touching a valve switch with your little finger. The valve amplified your finger motion to mash Chevys. But actually it was the hundreds-HP haudraulic supply which provided the increased wattage. With NPNs, same idea. Transistors are valves for flowing charge instead of flowing haudraulic fluid. What is my understanding is that for a transistor to amplify you need to bias it properly.

Forward biasing of BE junction makes it a conducting diode so input resistance is less. Reverse biasing CE junction makes it non conducting diode so output resistance is high. And if Ic is almost equal to Ie then the current causes a low voltage drop at input and large one at output. This is why its called an Amplifier. With a transistor, you can achieve this: Give a small signal ac at input, and get a larger valued higher amplitude signal at output.

But this is not all. You have to give DC supply at collector and base; emitter if required. This is called biasing the dc point. The rms power you get at the output will be less than the dc power you have supplied. DC analysis: don't consider any ac signal. Find out the values of all diode currents based on dc voltage at various nodes Collector, base , emitter. This is done by using KVL along various loops. Going further, the diode has forward resistance. So the actual model will be like this:.

From DC analysis, you must have found the value of Ie. Vout will depend on Ic. Ic will depend on Ib. Ib will depend on Vin and Re. Re we have found from DC analysis. Power steering amplifies the force of your arms. Power brakes amplify the force of your foot. On the other hand, a transformer is like a lever.

A step-up transformer converts to higher voltage at lower current and a step-down transformer reduces the voltage and increases the current. Note that I'm talking about AC transformers, not DC power supplies which can sometimes be quite a bit less efficient. But they do, but not as often because amplifying a digital signal is normally called "fanout" or "buffering" or "boosting".

There's nothing mere about controlling, that's how nearly all amplifiers work lasers and masers are the exception. What's amplified is the power in the signal, we don't care whether that signal shares a power supply with the input signal, we only care about the actual signal. It sounds to me you are stuck on the definition of amplification as "literally" increasing the power of the signal. It does not. Maybe you are misunderstanding the term analogue in analogue amplifier.

In recent times the word has become to mean the opposite of digital that is a continuous function instead of a discreet function.

But that is not what it really means. The current flowing from collector to emitter in a transistor is an analogue of the current flowing in the base to emitter. That is it is "like" the current but subject to some function, the simplest of which is gain, the multiplication by a constant. Rather than a relay being an amplifier, it is in fact the amplifier that is acting like a switch when you are dealing with digital signals.

However, unlike tubes and transistors, a relay cannot produce a variable output; It can only switch on and off similar to a logic circuit in a computer. But the relay has the advantage of being able to completely isolate its input circuit from its output. A transistor, by itself can't do anything at all, except being a paper weight for a very small piece of paper. What we can do with the transistor depends on what is connected to it.

For some circuits, involving transistors connected to resistors, and wires, and DC power source, and some capacitors, and a sinusoidal source supplying a relatively small sinusoidal signal people can create a voltage amplifier How does it manage to achieve this? The answer comes out by learning or finding out about general behaviours of the transistor, and basic circuit theory involving transistors and resistors and voltages and currents.

Circuit theory can allow some nice equations to be derived that allows you to predict in advance the amplification factor in terms of some component values or values related to the components. Other circuits allow the transistor's current amplification feature to be studied. For some conditions, if a DC voltage is applied to collector terminal while the emitter terminal is grounded, and a relatively small DC current is deliberately made to flow into the base after some particular experimental setup is carried out of course Hence it is observed that a change of 0.

As the common emitter mode of connection is mostly adopted, let us first understand a few important terms with reference to this mode of connection. As the input circuit is forward biased, the input resistance will be low. The input resistance is the opposition offered by the base-emitter junction to the signal flow. The output resistance of a transistor amplifier is very high. The collector current changes very slightly with the change in collector-emitter voltage.

The load is connected at the collector of a transistor and for a single-stage amplifier, the output voltage is taken from the collector of the transistor and for a multi-stage amplifier, the same is collected from a cascaded stages of transistor circuit. By definition, it is the total load as seen by the a.

A transistor consists of three layers of a semiconductor material. Those layers are capable of carrying a current. Transistors are devices that can amplify a signal in a circuit. It is normally made of germanium or silicon layers. A transistor requires very little current to operate so, releases very little heat. However, heat also depends upon it configuration. It is used in different things, such as an amplifier, oscillator, rectifier, switch, etc. A signal is just a general term used to refer to any particular current, voltage, or power in a circuit.

A mplification is a ratio between two values which does not imply that the output value is greater than the input value. Transistors are normally used as amplifiers. Some transistor circuits are current amplifiers, with a small load resistance, other circuits are designed for voltage amplification and have a high load resistance and others amplify power.