查看“︁哈特莱振荡器”︁的源代码

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|1=zh-hans:共漏; zh-hant:共汲極;
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'''哈特萊振盪器'''（{{lang-en|Hartley oscillator}}），又稱'''赫特利振盪器'''，'''电感三点式振荡器'''<ref>{{Citation| last =康华光 | date =2014-12 | title =电子基础技术.模拟部分 | edition =6th | place =北京 | publisher =高等教育出版社 | isbn =978-7-04-038480-2}}</ref>，是一種由[[电容器|电容]]和[[电感元件|电感]]的[[LC电路|调谐电路]]（即LC振荡器）决定振荡频率的[[电子振荡器]][[電子電路|电路]]。该电路是美国工程师{{le|雷夫·哈特萊|Ralph Hartley}}於1915年發明的。Hartley振荡器的特点是调谐电路由一个电容器与串联的两个电感（或单抽头电感）并联，振荡所需的[[反馈]]信号取自两电感连接的中心。

==操作==

[[Image:Hartley osc.svg|framed|共漏哈特萊电路]]

Hartley振荡器的突出特点是[[LC电路|谐振电路]]包含两个串联[[电感元件|线圈]]（或者通常用[[高阻态|抽头]]线圈）与电容器并联，在相对[[高阻态]]的LC槽电路和线圈间，相对低电压/高电流点之间有一个放大器。

1905年的原始版本使用一个[[三极管 (真空管)|三极管]]作为[[放大器|屏极接地]]（阴极跟随器）组态中的放大器件，含有三节电池，以及独立可调线圈。右图显示的简化电路使用一个[[结型场效应管|JFET]]（[[共漏极]]组态）、一个LC谐振电路（这里的单绕组是抽头的）和一个单电池。该电路说明了Hartley振荡器的操作：{{dubious|Circuit operation|reason=Many subtle problems with description such as JFET gm, Q killing, and lossless elements "absorbing" signals off resonance|date=2015年8月}}

* JFET的''源极''（若使用[[双极性晶体管|BJT]]则是''发射极''；三极管则是''阴极''）的输出与它的栅极（基极）的信号同[[相位]]，电压与它的输入（整个槽电路两端的电压）粗略相等，但''电流被放大了''，即它是作为[[缓冲放大器|电流缓冲器]]或{{le|Sallen–Key拓扑|Sallen–Key topology|电压控制电压源}}。
* 然后这个低阻态输出送入到线圈抽头中，有效地进入一个可以提高电压的[[自耦变压器]]，需要比较高的电流（相对于线圈顶部的电流来说）。
{{trans H}}
* with the capacitor-coil [[共振|resonance]], all frequencies other than the tuned frequency will tend to be absorbed  (the tank will appear as nearly 0Ω near DC due to the inductor's low [[电抗|reactance]] at low frequencies, and low again at very high frequencies due to the capacitor); they will also shift the phase of the feedback from the 0° needed for oscillation at all but the tuned frequency.

Variations on the simple circuit often include ways to [[Automatic Gain Control|automatically]] reduce the amplifier gain to maintain a constant output voltage at a level below overload; the simple circuit above will limit the output voltage due to the gate conducting on positive peaks, effectively damping oscillations but not before significant distortion ([[Spurious tone|spurious]] [[谐波|harmonics]]) may result. Changing the tapped coil to two separate coils, as in the original patent schematic, still results in a working oscillator but now that the two coils are not [[magnetically coupled]] the inductance, and so frequency, calculation has to be modified (see below), and the explanation of the voltage increase mechanism is more complicated than the autotransformer scenario.

A quite different implementation using a tapped coil in an LC tank feedback arrangement, still called a Hartley oscillator (or sometimes "the" Hartley Oscillator circuit<ref>http://www.learnabout-electronics.org/Oscillators/osc21.php {{Wayback|url=http://www.learnabout-electronics.org/Oscillators/osc21.php |date=20150920023644 }} The Hartley Oscillator</ref>) is to employ a common-grid (or common-gate or common-base) amplifier stage, which is still [[non-inverting]] but provides ''voltage gain'' instead of ''current gain''; the coil tapping is still connected to the cathode (or source or emitter), but this is now the (low impedance) input to the amplifier; the split tank circuit is now dropping the impedance from the relatively high output impedance of the plate (or drain or collector).

[[File:Oscillator comparison.svg|thumb|Comparison of Hartley and Colpitts oscillator]]
The Hartley oscillator is the dual of the [[Colpitts振盪器|Colpitts oscillator]] which uses a voltage divider made of two capacitors rather than two inductors.  Although there is no requirement for there to be mutual coupling between the two coil segments, the circuit is usually implemented using a tapped coil, with the feedback taken from the tap, as shown here. The optimal tapping point (or ratio of coil inductances) depends on the amplifying device used, which may be a [[双极性晶体管|bipolar junction transistor]], [[场效应管|FET]], triode, or amplifier of almost any type (non-inverting in this case, although variations of the circuit with an earthed centre-point and feedback from an [[inverting amplifier]] or the collector/drain of a transistor are also common), but a [[结型场效应管|junction FET]] (shown) or triode is often employed as a good degree of amplitude stability (and thus [[失真|distortion]] reduction) can be achieved with a simple [[grid leak]] <!-- is grid-leak confusing here? Hope not --> resistor-capacitor combination in series with the gate or grid (see the Scott circuit below) thanks to [[二極管|diode]] conduction on signal peaks building up enough [[PN结|negative bias]] to limit amplification.
{{trans F}}
[[Image:Oscillator hartley opamp.svg|thumb|235px|Hartley振荡器的运算放大器版本]]

振荡频率约为槽电路的[[共振|谐振频率]]。若槽路电容器的电容为 ''C'' 而抽头电感的总[[电感]]是 ''L''，则
:<math>f =  {1 \over 2 \pi \sqrt {LC}} \,</math>
若使用了电感为 ''L''<sub>1</sub> 和 ''L''<sub>2</sub> 两个''非耦合''的线圈
:<math>L = L_1 + L_2 \,</math>
然而，如果两个线圈磁耦合，总电感会因[[电感|互感]] ''k'' 而增大<ref>Jim McLucas, Hartley oscillator requires no coupled inductors, EDN October 26, 2006 {{cite web |url=http://www.edn.com/article/CA6343253.html |title=存档副本 |accessdate=2008-12-10 |deadurl=yes |archiveurl=https://web.archive.org/web/20080704153045/http://www.edn.com/article/CA6343253.html |archivedate=2008-07-04 }}</ref>
:<math>L = L_1 + L_2 + k \sqrt{L_1 L_2} \,</math>
由于线圈中的[[寄生电容]]和晶体管的负载，实际振荡频率将略低于上述。

Hartley振荡器的优点包括：

* 频率可以使用一个可变电容器进行调整，电容器的一边可接地
* 输出幅度保持恒定的频率范围内
* 需要一个抽头线圈或两个固定电感，以及很少的其他组件
* Easy to create an accurate fixed-frequency [[crystal oscillator]] variation by replacing the capacitor with a (parallel-resonant) [[石英|quartz crystal]] or replacing the top half of the [[LC电路|tank circuit]] with a crystal and grid-leak resistor (as in the [[Tri-tet oscillator]]).

缺点包括：

* 如果从放大器，而不是直接从LC电路（除非采用振幅稳定电路），则会得到谐波丰富的输出。

== 参见 ==
* {{le|光电振荡器|Opto-electronic oscillator}}

== 参考文献 ==
{{Reflist}}
*{{Citation
 |inventor-first= Ralph Vinton Lyon
 |inventor-last= Hartley
 |title= Oscillation Generator
 |description=
 |country-code= US
 |patent-number= 1356763
 |issue-date= October 26, 1920
 |publication-date= June 1, 1915
 |doi=}}
*{{Citation
 |first= F.
 |last= Langford-Smith
 |title= Radiotron Designer's Handbook
 |edition= 4th
 |year= 1952
 |publisher= Amalgamated Wireless Valve Company Pty., Ltd.
 |location= Sydney, Australia
 |isbn=
 |doi=}}
*{{Citation
 |first= F. A.
 |last= Record
 |first2= J. L.
 |last2= Stiles
 |title= An Analytical Demonstration of Hartley Oscillator Action
 |journal= Proceedings of the IRE
 |volume= 31
 |issue= 6
 |date= June 1943
 |issn= 0096-8390
 |doi= 10.1109/jrproc.1943.230656 }}
*{{Citation
 |first1= Ulrich L.
 |last1= Rohde
 |first2= Ajay K.
 |last2= Poddar
 |first3= Georg
 |last3= Böck
 |title= The Design of Modern Microwave Oscillators for Wireless Applications: Theory and Optimization
 |publisher= John Wiley & Sons
 |location= New York, NY
 |date= May 2005
 |isbn= 0-471-72342-8
 |doi= }}  
*{{Citation
 |first= George
 |last= Vendelin
 |first2= Anthony M.
 |last2= Pavio
 |first3= Ulrich L.
 |last3= Rohde
 |title= Microwave Circuit Design Using Linear and Nonlinear Techniques
 |publisher= John Wiley & Sons
 |location= New York, NY
 |date= May 2005
 |isbn= 0-471-41479-4
 |doi= }}

== 外部链接 ==
* [https://web.archive.org/web/20031102071209/http://www.tpub.com/content/neets/14181/css/14181_81.htm Hartley oscillator], Integrated Publishing

[[Category:振荡器]]