July 25, 2024

Vacuum tube Vs.Transistor ( Advantages & disadvantages)

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If you are finding the difference between the vacuum tube and transistor then you are at right place.  here we create a post related to transistor versus vacuum tube and going to compare transistor and vacuum tube.  We will also see a vacuum tube and transistor advantages and disadvantages and some advantages of the transistor over vacuum tubes.

In the past when the transistor was not invented then vacuum tube used in many applications but after the invention of the transistor, transistor takes place in most all places of vacuum tubes usage.

Now we are going to compare the vacuum tube and transistor with their advantages and disadvantages.


A brief comparison between the vacuum tube and transistor :

Now here we see in a brief comparison between both. Conceptually there is no difference between vacuum tubes and field effect transistor or MOSFET integrated circuits. But there is a difference between some physical matters of engineering like size, weight, voltage rating, heat etc.

Let see some brief comparison between this two,

Transistor Vacuum tube
  • Lower power consumption, less wastage of heat
  • Power consumption is high and heat wastage is comparatively high
  • Size is so small as compared to vacuum tubes.
  • Large size than transistor
  • Low cost.
  • High cost.
  • Easily portable device.
  • Less suitable for portable products.
  • It requires a lower power supply, suitable for smaller voltage devices
  • It requires the high voltage power supply, not suitable for smaller voltage devices.
  • High efficiency than vacuum tubes in small signal circuits
  • Not that much suitable for small signal circuits.
  • Physical strength is high
  • There is glass tube in a vacuum tube so not that much physical strength.
  • High voltage gain
  • Low voltage gain
  • Low input impedance
  • High input impedance
  • Depend upon Temperature
  • Not that much depend upon temperature
  • Relatively maintenance more difficult, cannot easily be replaced by a user.
  • Vacuum tubes can easily be replaced by a user
  • Made up of PN junction.
  • Made up of wires.

After this part, we will see almost all the advantages and disadvantages of the transistor over vacuum tubes.

Advantages of the transistor over vacuum tubes

The transistor is a solid state device which performs the same applications as vacuum tubes. However, due to some advantages over vacuum tubes transistors take place in the most area where vacuum tubes were used before the transistor invented. Here are some advantages:

1. High voltage gain :

We can able to get much higher voltage gain with transistor than vacuum tubes. In triode amplifier voltage gain is normally under 70 or 75. But in transistor amplifiers provides voltage gain up to 300 or more which is comparatively much high than vacuum tubes. Because of this advantage, transistors are now used in many amplifier circuits.

2. Low voltage supply :

Transistor device requires much smaller D.C supply to run in their applications. In other hand, vacuum tubes require to run with d.c voltage ranging from 400 V to 500 V. Vacuum tubes require much higher power than transistor device. This is the main advantages of the transistor which makes transistor portable and lightweight equipment. Vacuum tubes are heavier equipment than transistor device.

3. No heating :

A transistor does not require heater wherever vacuum tubes only works with a heater. The heater requirement in vacuum tubes posses many problems. it makes power supply bulky and there are also problems in getting rid of that heat. Because of heater vacuum tubes have a limit of useful life. In other side, transistors permanently soldered into circuits and it has a much longer life than vacuum tubes. Transistor lasts long for many years without any problems.

4. other advantages :

Apart from the above major advantages, there are also some miscellaneous advantages which make transistor superior to vacuum tubes:

  • Size: Transistor is so much smaller than vacuum tubes. This makes transistor circuits light-weight and easily portable. Vacuum tube has much weight than a transistor that makes the circuit heavier and not comfortable for portable control circuits.
  • Mechanical strength: Transistor is a solid state device wherever vacuum tubes outer layer is made p with glass. So there are chances of breaking this glass. So the transistor is mechanically so strong as compared to vacuum tubes.
  • Transistor is integrated with resistor and other diodes or electronics components and make an Ic circuit which is so small in size.

Disadvantages of the transistor over vacuum tubes

Although transistor maintains superiority over vacuum tubes but yet there are some drawbacks also in the transistor. Let see disadvantages of the transistor over vacuum tubes :

1. Lower power dissipation :

The transistor is not used in high power applications. The main reason behind this is lower power dissipation of the transistor device. Most power transistors have power dissipation is lower than 300 W. In other side vacuum tubes can power dissipation in kW. So for this reason transistor cannot be used in high power applications e.g transmitters, industrial control systems, microwave systems etc. In this all high power applications mainly vacuum tubes are used.

2. lower input impedance :

There are many electrical applications where we require high input impedance e.g. electric voltmeters, oscilloscope etc. In such applications, the transistor is not going to use. Transistor has a low input impedance which is not wealthy for such applications. Vacuum tubes are used in these types of equipment because vacuum tubes have high input impedance.

[ It may be noted here that here we talk about simple BJT transistor. If we talk about FET ( field effect transistor ) then FET has high input impedance and can replace vacuum tube in almost all applications ]

3. Temperature dependence :

Solid state device is dependent on temperature. The transistor is a solid state device and dependent on temperature effect. A slight change in temperature can cause a significant change in characteristics of the transistor device. It is a major disadvantage of the transistor.

4. Variation of parameters :

The manufacture of solid state devices (such as a transistor ) is a difficult process. In spite of best efforts of manufacturing, the parameter of transistors are not the same in all the time even transistors of the same batch.  For example. The B147 transistor has β may vary from 100 to 600.


here we compared transistor and vacuum tubes. Transistor and vacuum tube both are almost same in conceptually. Transistors are used in small integrated circuits which require low voltage supply and Vacuum tubes are used in high power applications. In the manner of size, the transistor is smaller than vacuum tubes. Vacuum tubes are really big and very hot. It uses lots of electricity. Transistor and vacuum tubes both have some advantages and disadvantages, we have to choose as per applications which we have to use in that manner.

Hope you understand really well about this topic transistor versus vacuum tube. if you have any doubt regarding this topic feel free to ask in a comment section. We will help you soon. Read also our related articles –

PNP transistor tutorial

NPN transistor tutorial

Common collector transistor configuration

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