Oscillators: Cad é sin? (Teorainn, Cineálacha, & Feidhmiú)
Cad é an Oscillator?
Is circuit é an oscillator a chuirtear ar fáil go leanúnach, atá i bhfeidhm go deichniúil, agus níl aon iontráil ann. D'fhéadfadh oscillators a athrú ar sciliú cinn díreach ó fhoinse DC go sciliú cothrománach a bhfuil an modh is mian leis, mar a shocrófar ag a chuid comhcheilt.
Is féidir an prionsabal bunúsach ina bhfuil oscilaithe ag obair a thuiscint trí an comportaíocht LC tank circuit a chur san áireamh, atá léirithe sa Figure 1 thíos, a úsáideann inductór L agus capacitor C a bhfuil sé ar fad pre-charged mar a chuid comhcheilt. Anseo, ar dtús, tosóidh an capacitor ag déanamh discharge trí an inductor, rud a chuironn suas do chonversion a chuid oibre leictreonach go réim eilemhithe, a stóráil sa inductor. Nuair a bheidh an capacitor déanta go hiomlán, ní bheidh aon sruth ag teacht i gciorcal.
Áfach, roinnt am éigin tar éis sin, beidh an réim eilemhithe stóráilte tar éis back-emf a chruthú a chuirfidh sruth ag teacht trí an gciorcal in an áit céanna lena raibh roimhe. Leanann an sruth ag teacht trí an gciorcal go dtí go ndéanfaidh an réim eilemhithe a chloisteoireacht, a chuirfidh ar ais an oibre leictreonach, agus a chuirfidh ar siúl an chluiche. Ach anois, beidh an capacitor charged le polaireacht contrártha, de bharr a mbaineann duine amach sciliú cothrománach mar an t-ionradh.
Áfach, ní féidir na hoscilaithe a thagann as an gcothrománach idir dhá fhoirm oibre a leanúint go deichniúil mar go mbeidh tionchar aontais air de bharr an t-aontas den gciorcal. Mar thoradh, leanann an méid seo ag dul síos go leanúnach go dtí zero, rud a dhéanann damped orthu.
Seo a léiríonn go gcaithfear aon aontas a chur ar fáil chun aon aontas a chur ar fáil. Ní mian leis an té aon aontas a chur ar fáil, ach caithfear a bheith rialta agus a bheith cothrom leis an aontas a chur ar fáil chun aon aontas a chur ar fáil.
Tá sé seo mar gheall ar, má tá an aontas a chuirtear ar fáil níos mó ná an aontas a chuirtear ar fáil, ansin leanann an méid seo ag dul suas (Figure 2a) ag tarlú output; áfach, dá mbeadh an aontas a chuirtear ar fáil níos lú ná an aontas a chuirtear ar fáil, ansin leanann an méid seo ag dul síos (Figure 2b) ag tarlú unsustained oscillations.
Go práinneach, níl oscillators ach an chuid amplifiers a chuirtear ar fáil le feedback positíf nó regenerative, áit a bhfuil cuid den output signal fed back go dtí an input (Figure 3). Anseo, cuirtear an amplifier ar fáil leis an gcomhcheilt amplifying active element, a bhfuil sé ina transistor nó Op-Amp, agus an signal in-phase fed back a chur ar fáil chun aon aontas a chur ar fáil trí aon aontas a chur ar fáil.
Nuair a cuirtear an cumhacht ar siúl, tosóidh an oscillations ag teacht sa chóras de bharr an noise leictreonach a bhfuil sé ann. Téann an signal noise timpeall an loop, agus a chuirfidh ar ais an oibre leictreonach agus a chuirfidh ar siúl an chluiche go tapa. Tá an expression don closed-loop gain den oscillator léirithe sa Figure 3:
Ansin, má tá Aβ > 1, ansin leanann an oscillations ag dul suas (Figure 2a); áfach, dá mbeadh Aβ < 1, ansin leanann an oscillations ag dul síos (Figure 2b). Ar an láimh eile, Aβ = 1 leanann an oscillations a bhfuil an aontas (Figure 2c). I bhfad eile, léiríonn sé seo go gcaithfear aon aontas a chur ar fáil chun aon aontas a chur ar fáil, agus aon aontas a chur ar fáil chun aon aontas a chur ar fáil.
Cineál Oscillator
Tá go leor cineál oscillators ann, ach is féidir iad a roinnt go forleathan i dtreo dhá chategóir phríomha – Harmonic Oscillators (chomh maith le Linear Oscillators) agus Relaxation Oscillators.
In a harmonic oscillator, the energy flow is always from the active components to the passive components and the frequency of oscillations is decided by the feedback path.
Whereas in a relaxation oscillator, the energy is exchanged between the active and the passive components and the frequency of oscillations is determined by the charging and discharging time-constants involved in the process. Further, harmonic oscillators produce low-distorted sine-wave outputs while the relaxation oscillators generate non-sinusoidal (saw-tooth, triangular or square) wave-forms.
The main types of Oscillators include:
Wien Bridge Oscillator
RC Phase Shift Oscillator
Hartley Oscillator
Voltage Controlled Oscillator
Colpitts Oscillator
Clapp Oscillators
Crystal Oscillators
Armstrong Oscillator
Tuned Collector Oscillator
Gunn Oscillator
Cross-Coupled Oscillators
Ring Oscillators
Dynatron Oscillators
Meissner Oscillators
Opto-Electronic Oscillators
Pierce Oscillators
Robinson Oscillators
Tri-tet Oscillators
Pearson-Anson Oscillators
Delay-Line Oscillators
Royer Oscillators
Electron Coupled Oscillators
Multi-Wave Oscillators
Oscillators can be also be classified into various types depending on the parameter considered i.e. based on the feedback mechanism, the shape of the output waveform, etc.. These classifications types have been given below:
Classification Based on the Feedback Mechanism: Positive Feedback Oscillators and Negative Feedback Oscillators.
Classification Based on the Shape of the Output Waveform: Sine Wave Oscillators, Square or Rectangular Wave oscillators, Sweep Oscillators (which produce saw-tooth output waveform), etc.
Classification Based on the Frequency of the Output Signal: Low-Frequency Oscillators, Audio Oscillators (whose output frequency is of audio range), Radio Frequency Oscillators, High-Frequency Oscillators, Very High-Frequency Oscillators, Ultra High-Frequency Oscillators, etc.
Classification Based on the type of the Frequency Control Used: RC Oscillators, LC Oscillators, Crystal Oscillators (which use a quartz crystal to result in a frequency stabilized output waveform), etc.
Classification Based on the Nature of the Frequency of Output Waveform: Fixed Frequency Oscillators and Variable or Tunable Frequency Oscillators.
Úsáid Oscillator
Oscillators are a cheap and easy way to generate specific Frequency of a signal. For example, an RC oscillator is used to generate a Low Frequency signal, an LC oscillator is used to generate a High Frequency signal, and an Op-Amp based oscillator is used to generate a stable frequency.
The frequency of oscillation can be varied by varying the component value with potentiometer arrangements.
Some common applications of oscillators include:
Quartz watches (which uses a crystal oscillator)
Used in various audio systems and video systems
Used in various radio, TV, and other communication devices
Used in computers, metal detectors, stun guns, inverters, ultrasonic and radio frequency applications.
Used to generate clock pulses for microprocessors and micro-controllers
Used in alarms and buzzes
Used in metal detectors, stun guns, inverters, and ultrasonic
Used to operate decorative lights (e.g. dancing lights)
