Oscillator Da Yawan Kashi | VCO

Voltage controlled oscillator (VCO), daga sunan da aka fi sani cewa yanayin karshe na mafi yawan frequency na oscillator yana kontrola da voltage ta hanyar input. Wannan wani abu ne na oscillator wanda zai iya samun output signal frequency a gaban yanki (daga hira-hirar Hertz zuwa hira-hirar Giga Hertz) tare da voltage DC ta hanyar input.

Frequency Control in Voltage Controlled Oscillator

An amfani da wasu hanyoyi na VCOs. Zai iya kasance RC oscillator ko multi vibrator ko LC ko crystal oscillator. Amma; idan yake da RC oscillator, frequency na output signal yana zama na nisa masu haske da capacitance kamar

A cikin LC oscillator, frequency na output signal yana zama
Saboda haka, zan iya ce idan voltage ta hanyar input ko control voltage ya zama, capacitance ya zama na nisa. Saboda haka, control voltage da frequency na oscillations suna da shawarwari. Yadda yakin hukuma, yakin biyu ya haɗa.

Takarda na farko yana nuna yadda voltage controlled oscillator ke yi aiki. A cikin wannan, za a iya tabbatar da cewa a nominal control voltage da aka nufin da VC(nom), oscillator yana yi aikinsu a frequency na free running ko normal, fC(nom). Idan control voltage ya nika min nominal voltage, frequency ya nika, saboda haka idan nominal control voltage ya zama, frequency ya zama.
An amfani da varactors diodes (wadannan su ne variable capacitance diodes [da ake samu a cikin yankin capacitance]) don samun voltage na yau. Don oscillators na frequency na nisa, an yi alamomin rate na charging na capacitors tare da voltage controlled current source don samun voltage na yau.

Types of Voltage Controlled Oscillator

VCOs zai iya faɗa a kan waveform na output:

• Harmonic Oscillators

• Relaxation Oscillators

Harmonic Oscillators

Waveform na output da harmonic oscillators ke samu shine sinusoidal. Wannan zai iya zama linear voltage controlled oscillator. Misaaluna suna da LC da Crystal oscillators. A cikin wannan, capacitance na varactor diode yana zama tare da voltage wanda yake cikin diode. Wannan yana zama capacitance na LC circuit. Saboda haka, frequency na output zai zama. Abubuwan da ake ƙara sun hada da frequency stability ta hanyar power supply, noise da temperature, Accuracy a kontrola frequency. Abin da ba ake ƙara shine wannan hanyoyi na oscillators ba su iya amfani da su a monolithic ICs.

Relaxation Oscillators

Waveform na output da harmonic oscillators ke samu shine saw tooth. Wannan hanyoyi zai iya bayyana yanki mai yawa tare da adadin components na nisa. Kafin amfani a monolithic ICs. Relaxation oscillators zai iya ƙunshi hanyoyin da suke:

• Delay-based ring VCOs

• Grounded capacitor VCOs

• Emitter-Coupled VCOs

A cikin delay-based ring VCOs, gain stages suna kasa a ring form. Kamar sunan, frequency yana da alaka da delay a baki daya. Hanyoyin biyu da uku sun yi aiki kamar haka. Time period na baki daya yana da shawarwari da time na charging da discharging na capacitor.

Working Principle of Voltage Controlled Oscillator (VCO)

VCO circuits zai iya fara da wasu voltage control electronic components kamar varactor diodes, transistors, Op-amps etc. A nan, za a tattauna game da aikin VCO tare da Op-amps. Circuit diagram shine ta haka.

Waveform na output ta hanyar VCO shine square wave. Daga cewa frequency na output yana da alaka da control voltage. A cikin wannan circuit, Op-amp na farko zai yi aiki a hanyar integrator. An yi arrangement na voltage divider a cikin wannan. Saboda haka, yakin biyar na control voltage wanda aka bayar a hanyar input ya bayar a terminal na positive na Op-amp 1. Level na biyar na voltage an yi amfani a terminal na negative. Wannan shine don sauki voltage drop a cikin resistor, R1 a biyar na control voltage.
Idan MOSFET yana cikin on condition, current wanda ya zama a R1 resistor ya zama a MOSFET. R2 yana da resistance na biyar, voltage drop na biyar da current na biyar a cikin R1. Saboda haka, current na biyar ya zama capacitor. Op-amp 1 yana bukata da output voltage na gradually increasing don samun current na biyar.
Idan MOSFET yana cikin off condition, current wanda ya zama a R1resistor ya zama a capacitor, get discharged. Output voltage wanda aka samu daga Op-amp 1 a wannan lokacin yana nika. Saboda haka, triangular waveform ya zama output na Op-amp 1.
Op-amp 2 zai yi aiki a hanyar Schmitt trigger. Input na Op-amp shine triangular wave wanda aka samu daga Op-amp 1. Idan input voltage yana da take da threshold level, output daga Op-amp 2 zai VCC. Idan input voltage yana da take da threshold level, output daga Op-amp 2 zai zero. Saboda haka, output na Op-amp 2 zai square wave.
Misaalun VCO shine LM566 IC ko IC 566. Wannan shine 8 pin integrated circuit wanda zai iya samun double outputs-square wave da triangular wave. Internal circuit shine ta haka.

Applications of Voltage Controlled Oscillator

• Function generator

• Phase Locked Loop

• Tone generator

• Frequency-shift keying

• Frequency modulation

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