آموزش Varicap or varactor diode

[SIMooRGH.M 496]

Varactor or varicap diodes are used mainly in radio frequency (RF) circuits to be able to provide a capacitance that can be varied by changing a voltage in an electronics circuit. This can be used for tuning circuits including radio frequency oscillators and filters.

 

Although both names: varactor and varicap diode are used, they are both the same form of diode. The name varactor meaning variable reactor, or reactance, and varicap meaning variable capacitance (vari-cap).

[SIMooRGH.M 496]

Operation of a variable capacitor

 

They key to understanding how a varactor or varicap diode works is to look at what a capacitor is and what can change the capacitance. As can be seen from the diagram below, a capacitor consists of two plates with an insulating dielectric between them.

 

 

The capacitance of the capacitor is dependent upon the area of the plates - the larger the area the greater the capacitance, and also the distance between them - the greater the distance the smaller the level of capacitance.

 

A reverse biased diode has no current flowing between the P-type area and the N-type area. The N-type region and the P-type regions can conduct electricity, and can be considered to be the two plates, and the region between them - the depletion region is the insulating dielectric. This is exactly the same as the capacitor above.

 

As with any diode, if the reverse bias is changed so does the size of the depletion region. If the reverse voltage on the varactor or varicap diode is increased, the depletion region of the diode increases and if the reverse voltage on varactor diode is decreased the depletion region narrows. Therefore by changing the reverse bias on the diode it is possible to change the capacitance.

 

 

[SIMooRGH.M 496]

Varactor or varicap circuit symbol

 

The varactor diode or varicap diode is shown in circuit diagrams or schematics using a symbol that combines the diode and capacitor symbols. In this way it is obvious that it is being used as a varacor or varicap capacitor rather than a rectifying diode.

 

 

 

Circuit symbol for a varactor diode / varicap diode

 

 

When operated in a circuit, it is necessary to ensure the varactor diode remains reverse biased. This means that the cathode will be positive with respect to the anode, i.e. the cathode of the varactor will be more positive than the anode.

[SIMooRGH.M 496]

Varactor circuits

 

It is impossible to show all the circuits in which varactor / varicap diodes may be used. However it is worth providing one example to show how these diodes may be used in a typical circuit. Effectively a capacitor is replaced with the varactor diode, but it is necessary to also ensure that the tune voltage, i.e. the voltage used to set the capacitance of the diode can be inserted into the circuit, and that no voltages such as bias voltages from the circuit itself can affect the varactor diode.

 

 

 

 

 

 

Voltage controlled oscillator using a varactor diode

 

Within this circuit D1 is the varactor diode that is used to enable the oscillator to be tuned. C1 prevents the reverse bias for the varactor or varicap diode being shorted to ground through the inductor, and R1 is a series isolating resistor through which the varactor diode tuning voltage or bias is applied.

[Mehdi.Aref 26780]

كار خوبي كردي اما اگه كمي توضيحي ميدادي يا ترجمشو ميذاشتي بهتر بود:ws2:

[SIMooRGH.M 496]

حتما توضیح باشه ولی

فک کنم ترجمش نکنم بهتر باشه

[peyman sadeghian 30244]

Varactor or varicap diodes are used mainly in radio frequency (RF) circuits to be able to provide a capacitance that can be varied by changing a voltage in an electronics circuit. This can be used for tuning circuits including radio frequency oscillators and filters.

 

Although both names: varactor and varicap diode are used, they are both the same form of diode. The name varactor meaning variable reactor, or reactance, and varicap meaning variable capacitance (vari-cap).

دیود واراکتورVaractor یا همون دیودvaricap عمدتادر مدارات فرکانس رادیویی(RF)برای تهیه کردن خازنی متغیربا ولتاژمداراستفاده میشود.که از آن میتوان درمدارات تنظیم کننده فرکانس یا همون تیونرهاازجمله نوسانسازهای فرکانسهای رادیویی وصافی ها استفاده کرد.

اگرچه هردو نام واراکتور و واریکپ برای این دیود استفاده میشودهردو شکل مشابهی از یک دیوداست.نام واراکتوریعنی راکتورمتغییر ،یامقاومت خازنی،وواریکپ یعنی خازن متغیر(vari-cap)

ترجمه توسط پیمان.ص

 

[peyman sadeghian 30244]

Operation of a variable capacitor

 

They key to understanding how a varactor or varicap diode works is to look at what a capacitor is and what can change the capacitance. As can be seen from the diagram below, a capacitor consists of two plates with an insulating dielectric between them.

 

 

The capacitance of the capacitor is dependent upon the area of the plates - the larger the area the greater the capacitance, and also the distance between them - the greater the distance the smaller the level of capacitance.

 

A reverse biased diode has no current flowing between the P-type area and the N-type area. The N-type region and the P-type regions can conduct electricity, and can be considered to be the two plates, and the region between them - the depletion region is the insulating dielectric. This is exactly the same as the capacitor above.

 

As with any diode, if the reverse bias is changed so does the size of the depletion region. If the reverse voltage on the varactor or varicap diode is increased, the depletion region of the diode increases and if the reverse voltage on varactor diode is decreased the depletion region narrows. Therefore by changing the reverse bias on the diode it is possible to change the capacitance.

 

 

عملکرد یک خازن متغیر:

کلید درک اینکه یک دیود واراکتور یا واریکپ چکونه کار میکند این است که ببینیم یک خازن چگونه ظرفیتش تغییر میکند.همانطور که از نمودار زیر می توان دید خازن شامل دو ورقه با عایق دی الکتریک بین آنها است.

 

ظرفیت خازن بستگی دارد به سطح مقطع صفحات-هرچه این سطح مقطع بزرگتر باشد ظرفیت خازن بیشتر است.وهمچنین بسته به فاصله بین این دو صفحه که هرچه این فاصله بیشتر باشد ظرفیت خازن کمتر میشود

دربایاس معکوس دیودهاهیچ جریانی بین دو منطقه PوNجریان تدارد...منطقه نوع Nومناطق نوعPمیتوانند جریان الکتریسیته را عیور دهند.پس میتوان مناطق PوNرا همان صفحات وفضای بین آنهارا همان دی الکتریک عایق در نظر گرفت که شبیه همان خازن بالاست.

مثل هردیودی،تغییردرولتاژمعکوس دیود تغییر در اندازه منطقه تخلیه را به همراه دارداگر ولتاژ معکوس دوسر دیود واراکتور افزایش یابدعرض منطقه تخلیه افزایش میابدواگر ولتاژمعکوس دوسردیودواراکتورکاهش یابد این منطقه نیز نازک میشود.پس با تغییرولتاژمعکوس دوسر دیود،تغییرظرفیت خازنی آن امکان پذیرخواهدبود

 

[peyman sadeghian 30244]

Varactor or varicap circuit symbol

 

The varactor diode or varicap diode is shown in circuit diagrams or schematics using a symbol that combines the diode and capacitor symbols. In this way it is obvious that it is being used as a varacor or varicap capacitor rather than a rectifying diode.

 

 

 

Circuit symbol for a varactor diode / varicap diode

 

 

When operated in a circuit, it is necessary to ensure the varactor diode remains reverse biased. This means that the cathode will be positive with respect to the anode, i.e. the cathode of the varactor will be more positive than the anode.

علامت مداری واراکتور یا واریکپ:

دیود واراکتور یا دیود واریکپ در مدارات وشماتیکها با سمبلی که از ترکیب سمبل خازن ودیود نشان داده میشودبه این ترتیب به وضوح دیودیکسوساز از دیودواراکتور قابل تشخیص خوهد بود

 

 

برای عمل کردن این دیود درمدار لازم است مطمئن شویم دیود دربایاس معکوس قراردارد این بدان معناست کهکاتد نسبت به آند مثبت تر باشد یعنی کاتد دیود واراکتور مثبت تر از آند آن خواهدبود.

 

ترجمه پیمان.ص