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Home / Technical Articles / Difference between step-up transformer and voltage amplifier

Voltage amplifier? Similar or not?

A step up transformer basically increases the magnitude of primary applied voltage that is increases the amplitude of voltage wave form. A voltage amplifier does exactly the same.

Altec Peerless 4722 MC Step-up transformer
Altec Peerless 4722 MC Step-up transformer

Than a very strange but thinkable question comes what is the difference between the two and can we use a small step up transformer in place of voltage amplifier and vice-versa?


Transformers are unable to amplify (step up) an ac input Voltage without reducing (stepping down) it`s current capability.Amplifier can amplify both current and Voltage at the same time. We can have 1V at 1uA to drive the input but might also get many volts at many Amps at the output.
Transformer`s coil windings never requires a dc Voltage to operate. Sometimes a dc Voltage might be present in a transformer winding for auxiliaries but the dc is not required for the operation of the transformer.Amplifier almost always requires a dc working supply Voltage to operate.
Transformer has more winding added to its secondary winding to obtain Voltage amplification.An Amplifier actually modulates a fixed dc source Voltage in response to an ac input Voltage to obtain output Voltage amplification.
A transformer`s input current is proportional to its load current.Amplifier’s input current is normally almost independent of its load current.
A transformer is like a gearbox, whereas an amplifier is like an engine. The gearbox converts energy like a transformer.Amplifier is like an engine, which consumes fuel to give output. Similarly amplifier consumed DC supply to give output.
A step up transformer can amplify a specified type of input which is the sinusoidal input or time varying input and add to that the range of input the transformer is very flexible in range.Amplifier can amplify any signal and while the amplifier would have a limited range then in the saturation state.
In an ideal transformer output impedance is equal to the source impedance times the square of the turns ratio.An amplifier can have output impedance that is independent of the source impedance.

How amplifier works - The concept
How amplifier works – The concept

Transformer is not an amplifier, because:

The output and input powers are same and there is not any another source other than the signal (that is incoming AC voltage), Amplifier can amplify the signal voltage without reducing the output current.

Transformer follows the principle of induction where as Amplifier follows the principle of boosting the signal (voltage or current). Actually, the amplifier generates a completely new output signal based on the input signal. We can understand these signals as two separate circuits.

The output circuit is generated by the amplifier’s power supply, which draws energy from a battery or power outlet.

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Asif Eqbal

Bachelor of Engineering in Electrical & Electronics engineering, from Manipal University, (Karnataka), India in 2006. Presently involved in the design of EHV outdoor substation and coal fired thermal power plants for more than seven years. Motto of joining EEP as a contributor is to share my little engineering experience and help the budding engineers in bridging the conspicuous gap between academics and Industrial practice. “If you have knowledge, let others light their candles with it, so that people who are genuinely interested in helping one another develop new capacities for action; it is about creating timeless learning processes".


  1. Venkata suriya Narayanan
    May 16, 2019

    Thank you Asif for your wonderful explanation

  2. Rick
    Oct 17, 2018

    This is a very well-written breakdown of the differences. I was googling because I was curious about this, and found your article! Thanks.

  3. fitz
    Jul 25, 2016

    I have built a circuit to control a single phase induction motor using PWM. I am getting an output of 12 volts ac 50 Hz but I need to obtain 230 volts to drive the motor. Is there a way to achieve this. Also if you have a circuit I can utilise would be grateful


  4. Ben
    May 12, 2016

    thank you :)

  5. Biswa Aich
    Nov 14, 2014

    Great explanation, havent found any other site describing it so preciesely and easily.

  6. Karen
    Apr 11, 2014

    Great post. This table reminds me of my college days. I recently picked up a step up transformer from, which I want to play around with, just in my spare time.

  7. rohitkumarindia
    May 09, 2012

    nice 1

  8. MKHAWA88
    Mar 26, 2012

    it is very simple comparison thanks alot

  9. Edvard
    Mar 17, 2012

    Nice and very concise explanation! Many thanks Asif!

    • Asif Eqbal
      Mar 18, 2012

      Thanks Edvard

      • alex
        Dec 01, 2020

        Can you help me on how to step-up a chassis engine’s voltage to power a microwave generator on a vehicle.

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