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An electromagnetic device for changing the voltage of alternating current electricity. Every transformer has a primary coil and one or more secondary coils. The primary coil receives electrical energy from a power source and couples this energy to the secondary coils by means of a changing magnetic field. The energy appears as an electromagnetic force across the coil, and if a load is connected to the secondary the energy is transferred to the load. The voltage at which electric power is used in motors and lamps is less than that required for distribution. It is necessary to raise the voltage at the generating station to the value required for transmission, which is called "step up" the voltage. Then to lower it at the point of consumption to the values required by the motors and lamps, which is called "step down". The transformer is what makes these changes in voltage.
But what is the basic difference and in what circumstances do we use the Step Up Transformer and the Voltage Amplifier?
Op amps amplify voltages just like transformers. But it does not output a lot of current. A transofrmer on the other hand can transfer lots of power to the secondary coils. That is why an op amp is never used to drive motors or provide a power rail. If you read the datasheet, the max output current is usually less than 100mA.
Main difference between step up transformer and amplifier is that transformer is passive component and amplifier consists basically of active elements such as transistors, fets or tubes and passive components. Step up transformer "amplifies" the signal because secondary winding has more turns than primary. Ratio of secondary and primary voltages is proportional to ratio of turns in secondary and primary windings Vp/Vs=Np/Ns. Amplifiers exploit the property of active devices which convert small input power signal to higher output power signal by converting DC power from supply.
Propably you mean as far as voltage output levels are concerned.
The step up transformer just rises the voltage according to the turns ratio. The power at the output is less than or equal (ideal transformer) to the power given at the input. That means I*V (input)=I*V (output) hence you have higher voltage but less current, hence it has a higher output impedance than that of input.
The voltage amplifier has simmillar characteristics but it could be of low output impedance (like the power amplifiers) so, it can have also a current amplification if it is designed so. The ratio of "Power input=Power output" does not apply here.
You can have 1V at 1uA to drive the input but you might get many volts at many Amps at the output.
Depending on the requirements of your design you may deside which one to use. Is up to the specific desinger and needs.
IanP got it right, but let me put it like this: A transformer is like a gearbox, whereas an amplifier is like an engine. The gearbox converts energy like a tranformer. You can have high revs, low torque in (high voltage, low current) and low revs, high torque out (low voltage, high current). The engine creates rpm and torque, but consumes fuel, the same way that an amplifier needs a power supply.
a step up transfoer can amplify a specified type of input which is the sinusoidal input as i know and if u want to amplify another type of input i donot know but there are some limitations with very narrow duration pulses ( check out the pulse transformer ) while the amplifier can amplify any signal and add to that the range of input the transformer is very flexible in range while the amplifier would have a limited range then itz in the saturation state ,
An amplifier can have an output impedance that is independent of the source impedance. A ideal transformer output impedance is equal to the source impedance times the square of the turns ratio.
For example, a transformer with a 1:100 voltage step-up (turns) ratio that is driven by an input with a source resistance of 1000 Ohms will have an output resistance of 1000 X (100^2) = 10,000,000 Ohms.