umery2k75
Advanced Member level 1
If I talk about Hartley,Collpit oscillator,square wave oscillator.In general, it's said feedback must be positive,in phase and the close loop gain must be greater than 1 and there are various feedbacks also in shape of current-series/shunt,voltage series-shunt.Also in some oscillator no input signal is needed to start the oscillator going.Only conditions must be satisfied for self-sustained oscillations to result.
In one book, I read "In practice, close loop gain is made greater than 1 and the system is started oscillating by amplifying noise voltage, which is always present"
In another book, I read " In an oscillator the loop gain AB is greater than 1 when the power is first turned on. A small starting voltage is applied to the input terminals, and the output voltage builds up. After the output voltage reaches a desired level, AB automatically decreases to 1, and the peak-to-peak output becomes constant..........Where does the starting voltage comes from? Every resistor contains some free electrons. Because of the ambient temperature,these free electron move randomly in different directions and generate a noise voltage across the resistor. The motion is so random that it contains frequencies to over 1000 GHz. You can think of each resistor as small ac voltage source producing all frequencies. When you first turn on the power, the only signals in the system are noise voltages generated by the resistors. These noise voltages are amplified and appear at the output terminals. the amplified noise drives the resonant feedback circuit. By deliberate design, we can make the phase shift around the loop equal to 0' at the resonant frequency. Above and below the resonant frequency, the phase shift is different from 0'. In this way, we get oscillation at only one frequency, the resonant frequency of the feedback circuit."
What if I don't have resistors in my oscillator. I don't know if resistors were 1000GHZ frequency generators. Does one have to go into the sub atomic physics to understand who start them into oscillation, as how electrons algins themselves. Or do I attach a high speed camera like oscilloscope to capture the output of the oscillator while turned on in slow motion.
What if my circuit is noise free? I remember there are so many types of noises like white noise,shot noise, nyquist noise.
In the internet,book there is fairly simple explanation of the oscillator in working. Like we might have formula governing them. loop gain,phase equation.Suppose for a wien bridge the notch frequency is fr=1/(2*pi*RC). How does this equation comes from when Mr.Wien design the oscillator. I think this is not the work of Electronic engineer, they must be physicst. The level of details that are present in the electronics books that I have,or the one that I have seen in libraries,stores contains only a certain level of information to get the basic understanding and to calculate some parameters. It never teaches in detail. However, I see there are hundreds of parameter that can be put into the above wien bridge oscillator formula like temperature,pressure, gravity(maybe),etc. Only If I make a complex model of the notch frequency of the Wein Bridge. Oscillators might be crystal clear to a phyicsist but not not as clear to an electronic engineer, who just know how to put things together. For now, I just want to know, you also think of resistors noise as a starter for a oscillator or you also take some another sub-atomic thing in nature and believe this will start the oscillator.
Like in classical phyiscs it was believed a revolving electron must emit electromagnetic radiation and fall into nuclues one day, but it was always getting energy from thermal,etc. I don't know from where but it was that keeping that atom alive. Then Bohr I think proposed the theory of discrete level of electron shells with the help of Spectrum analysis, by the jumping of electrons. We always make an assumtion to saistfy something. I don't know if this concept is an assumption or relaity. Like we say in earlier time about conventional/electronic current flow. Electronics doesn't go into physics level, it is not on low level. Today I am getting irritated by oscillators, I don't know why, please share your views. What you think.
In one book, I read "In practice, close loop gain is made greater than 1 and the system is started oscillating by amplifying noise voltage, which is always present"
In another book, I read " In an oscillator the loop gain AB is greater than 1 when the power is first turned on. A small starting voltage is applied to the input terminals, and the output voltage builds up. After the output voltage reaches a desired level, AB automatically decreases to 1, and the peak-to-peak output becomes constant..........Where does the starting voltage comes from? Every resistor contains some free electrons. Because of the ambient temperature,these free electron move randomly in different directions and generate a noise voltage across the resistor. The motion is so random that it contains frequencies to over 1000 GHz. You can think of each resistor as small ac voltage source producing all frequencies. When you first turn on the power, the only signals in the system are noise voltages generated by the resistors. These noise voltages are amplified and appear at the output terminals. the amplified noise drives the resonant feedback circuit. By deliberate design, we can make the phase shift around the loop equal to 0' at the resonant frequency. Above and below the resonant frequency, the phase shift is different from 0'. In this way, we get oscillation at only one frequency, the resonant frequency of the feedback circuit."
What if I don't have resistors in my oscillator. I don't know if resistors were 1000GHZ frequency generators. Does one have to go into the sub atomic physics to understand who start them into oscillation, as how electrons algins themselves. Or do I attach a high speed camera like oscilloscope to capture the output of the oscillator while turned on in slow motion.
What if my circuit is noise free? I remember there are so many types of noises like white noise,shot noise, nyquist noise.
In the internet,book there is fairly simple explanation of the oscillator in working. Like we might have formula governing them. loop gain,phase equation.Suppose for a wien bridge the notch frequency is fr=1/(2*pi*RC). How does this equation comes from when Mr.Wien design the oscillator. I think this is not the work of Electronic engineer, they must be physicst. The level of details that are present in the electronics books that I have,or the one that I have seen in libraries,stores contains only a certain level of information to get the basic understanding and to calculate some parameters. It never teaches in detail. However, I see there are hundreds of parameter that can be put into the above wien bridge oscillator formula like temperature,pressure, gravity(maybe),etc. Only If I make a complex model of the notch frequency of the Wein Bridge. Oscillators might be crystal clear to a phyicsist but not not as clear to an electronic engineer, who just know how to put things together. For now, I just want to know, you also think of resistors noise as a starter for a oscillator or you also take some another sub-atomic thing in nature and believe this will start the oscillator.
Like in classical phyiscs it was believed a revolving electron must emit electromagnetic radiation and fall into nuclues one day, but it was always getting energy from thermal,etc. I don't know from where but it was that keeping that atom alive. Then Bohr I think proposed the theory of discrete level of electron shells with the help of Spectrum analysis, by the jumping of electrons. We always make an assumtion to saistfy something. I don't know if this concept is an assumption or relaity. Like we say in earlier time about conventional/electronic current flow. Electronics doesn't go into physics level, it is not on low level. Today I am getting irritated by oscillators, I don't know why, please share your views. What you think.
