Amplifiers: Important Parameters of Amplifier

Amplifier Feature
Amplifier Feature

What is an Amplifier?

Amplifier, In Electronics, Signal processing is very much essential. Signal Processing includes improving desired Signals and attenuating (removing) unwanted/noise signals. And there are possibilities that desired signals aren’t of desired amplitude, during these conditions use of amplifier become essential.

Amplifier in basic term is a circuit which boosts the voltage level of input signal to predefined voltage levels. The resultant voltage levels are determined by the gain of amplifier. So we can conclude that an Amplifiers are electronic circuits which introduces some gain to input signal.

Why use Amplifiers?

Amplifier is basically used everywhere in electronics. Various common examples of application are Sound Amplifiers, in Signal Generators, Televisions and many more. In some applications, it is essential that input voltage should have certain threshold value to drive particular load. If voltage levels aren’t sufficient it may fail while driving the load. In order to overcome this condition, an amplifier is used which brings up the voltage levels to certain required amplitude. For Eg: Consider a Sound System having input from a mobile phone. Voltage levels from mobile phones aren’t sufficient to drive loud speakers in Sound Sytsem. So we use amplifiers which boosts the amplitude of signal to an extent that it can drive loud speakers.

Note: 

  1. Amplifiers can only be used where input voltage is Alternating in nature
  2. Ideal Amplifiers produce exactly similar output waveform as fed in input, shape of waveform doesn’t change. Only Amplitude increases.
Amplifier Output
Amplifier’s Output

As we can observe in above figure, only amplitude has increased, waveform remains the same.

Important Parameters of Amplifiers:

Listed below are some important factors which should be considered while designing or purchasing amplifiers.

  1. Amplification factor/ Gain of Amplifiers:

Amplification factor or gain of  amplifiers determines the factor by which the input voltage will be boosted. For eg. If an amplifier with gain of 10 is fed with 2V output will be 20V. Utmost care should be taken while determining gain of amplifiers, if should have sufficient gain to drive the appliance/application

2. Supply Voltage:

Every amplifier requires some DC input voltage for biasing the amplifier components. These supply is essential for creating amplification conditions. It can be co-related with Vcc used in most electronic circuit. This is another important factor while selecting/designing Amplifiers.

Important: Peak Amplitude of Output Voltage of Amplifiers will never be more than Supply Voltage

Thus if supply voltage is 10V and even is gain is 10 while input is 2V you will get only 10V peak-peak at Output. So it is important to determine Supply Voltage carefully.

3. Bandwidth of Amplifiers:

Bandwidth of an Amplifiers is the range of frequencies, of input within which the amplifiers provides desired gain. It is important to have a bandwidth consisting of all range of input frequencies. For frequencies outside bandwidth amplifier provides negligible gain.

4. Input & Output Impedance of Amplifiers:

Input Impedance of Amplifiers is the input resistance offered by the amplifier. It should be as high as possible to avoid loading effect. Output Impedance is output resistance of amplifiers, it should be as low as possible to avoid loading effect in further stages/load.

5. Loading Effect in Amplifiers:

Loading effect is very critical phenomenon which needs to be considered while using an amplifier. Loading Effect is generally co-related with low input impedance. Let’s understand Loading Effect. Consider an Amplifier with low input impedance,  A source of 3Vpp,100mA is used to feed input to amplifier. When this source is connected, Amplifier tends to used maximum current possible. In the process current>100mA starts moving towards input, as source is only rated 100mA when current>100mA is drawn the voltage (3V) drastically drops tending to zero. This creates complete loss of input, in order to avoid these Input Impedance should be maximum.

Loading effect in Output of Amplifiers:

As load is connected to output of Amplifiers, we need maximum power to be delivered to load if desirable power isn’t delivered to load it may lead to improper driving of load. In order to avoid this Output Impedance should be maximum.

 

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