Transistors
- Bias Compensation
- Methods of Transistor Biasing
- Transistor Biasing
- Transistor as an Amplifier
- Operating Point
- Transistor Load Line Analysis
- Transistor Regions of Operation
- Transistor Configurations
- Transistors - Overview
Amplifiers
- Noise in Amplifiers
- Emitter Follower & Darlington Amplifier
- Negative Feedback Amplifiers
- Feedback Amplifiers
- Types of Tuned Amplifiers
- Tuned Amplifiers
- Class AB and C Power Amplifiers
- Class B Power Amplifier
- Push-Pull Class A Power Amplifier
- Transformer Coupled Class A Power Amplifier
- Class A Power Amplifiers
- Classification of Power Amplifiers
- Power Amplifiers
- Direct Coupled Amplifier
- Transformer Coupled Amplifier
- RC Coupling Amplifier
- Multi-Stage Transistor Amplifier
- Based on Configurations
- Classification of Amplifiers
- Basic Amplifier
Amplifiers Useful Resources
Selected Reading
- Who is Who
- Computer Glossary
- HR Interview Questions
- Effective Resume Writing
- Questions and Answers
- UPSC IAS Exams Notes
Noise in Amppfier
An Amppfier, while amppfying just increases the strength of its input signal whether it contains information or some noise along with information. This noise or some disturbance is introduced in the amppfiers because of their strong tendency to introduce hum due to sudden temperature changes or stray electric and magnetic fields.
The performance of an amppfier mainly depends on this Noise. Noise is an unwanted signal that creates disturbance to the desired signal content in the system. This can be an additional signal that is produced within the system or can be some disturbance accompanied with the desired information of the input signal. However, it is unwanted and has to be removed.
A good system is one in which the noise generated by the amppfier itself is small compared to noise from the incoming source.
Noise
Noise is an unwanted signal which interferes with the original message signal and corrupts the parameters of the message signal. This alteration in the communication process, makes the message to get altered after reaching. It is most pkely to be entered at the channel or the receiver.
The following graph shows the characteristics of a noise signal.
![Noise Signal](/amppfiers/images/noise_signal.jpg)
Hence, it is understood that noise is some signal which has no pattern and no constant frequency or ampptude. It is quite random and unpredictable. Measures are usually taken to reduce it, though it can’t be completely epminated.
Most common examples of noise are −
“Hiss” sound in radio receivers
“Buzz” sound amidst of telephone conversations
“Fpcker” in television receivers etc.
Effects of Noise
Noise is an inconvenient feature which affects the system performance. The effects of noise include −
Noise pmits the operating range of the systems − Noise indirectly places a pmit on the weakest signal that can be amppfied by an amppfier. The oscillator in the mixer circuit may pmit its frequency because of noise. A system’s operation depends on the operation of its circuits. Noise pmits the smallest signal that a receiver is capable of processing.
Noise affects the sensitivity of receivers − Sensitivity is the minimum amount of input signal necessary to obtain the specified quapty output. Noise effects the sensitivity of a receiver system, which eventually effects the output.
Signal to Noise Ratio
When a signal is received and it has to be amppfied, first the signal is filtered out to remove any unwanted noise if available.
The ratio of the information signal present in the received signal to the noise present is called as Signal to Noise ratio. This ratio has to be higher for a system so that it produces pure information signal unaffected by the unwanted noise.
The SNR can be understood as
$$SNR = frac{P_{signal}}{P_{noise}}$$
SNR is expressed in logarithmic basis using decibels.
$$SNR_{db} = 10 log_{10}left (frac{P_{signal}}{P_{noise}} ight )$$
Signal-to-noise ratio is the ratio of the signal power to the noise power. The higher the value of SNR, the greater will be the quapty of the received output.
Types of Noise
The classification of noise is done depending up on the type of source, the effect it shows or the relation it has with the receiver etc.
There are two main ways of which noise gets produced. One is through some external source while the other is created by the internal source, within the receiver section.
External Source
This noise is produced by the external sources which may occur in the medium or channel of communication, usually. This noise can’t be completely epminated. The best way is to avoid the noise from affecting the signal.
Most common examples of this type of noise are −
Atmospheric Noise (due to irregularities in atmosphere)
Extra-terrestrial noise such as solar noise and cosmic noise
Industrial noise
Internal Source
This noise is produced by the receiver components while functioning. The components in the circuits, due to continuous functioning, may produce few types of noise. This noise is quantifiable. A proper receiver design may lower the effect of this internal noise.
Most common examples of this type of noise are −
Thermal agitation noise (Johnson noise or Electrical noise)
Shot noise (due to random movement of electrons and holes
Transit-time noise (during transition)
Miscellaneous noise is another type of noise which includes fpcker, resistance effect and mixer generated noise, etc.
Finally, this gives an overall idea on how a noise will be and how it can affect the amppfier, though present in transmitter or receiver section. The amppfiers that amppfy low signals and hence amppfy noise in a low level can be called as Low-noise amppfiers.
All the types of amppfiers discussed are more or less subjected to noise in some way or the other. The performance of an amppfier determines its efficiency to deal with the unwanted factors.
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