How do transistors amplify

By definition, it is the total load as seen by the a. In case of single stage amplifiers, the effective collector load is a parallel combination of R C and R o. In a multi-stage amplifier i. Effective collector load becomes parallel combination of R C , R o and R i i. The gain in terms of current when the changes in input and output currents are observed, is called as Current gain.

The gain in terms of voltage when the changes in input and output currents are observed, is called as Voltage gain. The gain in terms of power when the changes in input and output currents are observed, is called as Power gain. Transistor as an Amplifier Advertisements. Previous Page.

Next Page. 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.

Considering the above diagram:. The small current travels from the voltage source into the base of the transistor. A current at the base turns on the transistor.

The current is then amplified and travels from the emitter of the transistor to the collector. The amplified current is large enough to turn on and light the LED. A separate power source must be connected to the collector of the transistor because a transistor is an active device, which means it needs power in order to operate.

The amplifier is complex circuit which is exploiting properties of a transistor. It has input node and output node. The output voltage from the amplifier, taken at the collector of Q1 with respect to the emitter, is a negative alternation of voltage that is larger than the input, but has the same sine wave characteristics.

During the negative alternation of the input signal, the transistor current increases because the input voltage aids the forward bias. The output for the negative alternation of the input is a positive alternation of voltage that is larger than the input but has the same sine wave characteristics.

I don't see how a transistor is "amplifying" anything. The collector and emitter are hooked up to a completely separate power source. For example, it's not taking the 0. How is this amplification? It's about as much "amplification" as my little Arduino is doing by sending a 5V signal to a relay that "amplifies" a V AC circuit connected on the other side, but I don't ever hear people say that a relay is amplifying voltage or current.

It seems to me that a transistor is merely controlling a greater voltage or current with its own smaller voltage and current. Am I missing something? I can't expect to take a single little 5V 1A power supply and through a transistor turn it into 12V or 5A, right? If the base current was 1mA and the gain was a collector current of mA 'could' flow. If your collector relay coil was ohms and the supply voltage was 5 volts, 5 -. If your collector resistor was ohms and the supply voltage was 5 volts, 5 -.

So using this definition of amplification, a relay is also amplifying current, just in a binary fashion compared to the Active operational mode of a transistor where the current from collector to emitter is proportional to the current flowing into the base.

A 40mA current on a relay pin coming from a 5V source gets amplified to a 5A VAC current when the relay switches on a microwave. A 5A current could flow if the relay had a 40mA current. In the case of the transistor that will be the ratio of collector current divided by base current. Of course, the conservation of energy always applies.

Yes, a relay is something like an amplifier. So is the gas pedal in your car When you drive your car, the strength of your foot isn't moving the car.

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.