201242237 六、發明說明： 【發明所屬之技術領域】 本發明是有關於一種振盪器，特別是指—種低功率消 耗的振盪器。 ' 【先前技術】 在許多高頻設備如手機的無線收發系統、高頻量測儀 器或類比數位廣播系統等應用中均有一個壓控振盪器用 以提供一將低頻率的原始訊號提升至較高頻率所需要的載 波，且該載波的輸出功率、振盪頻率、調變範圍及相位雜 訊皆關係著接收機的解調能力，所以一種具有低功率消耗 能延長如手機等可攜式行動產品的電力續航力，且又能提 供以上所述特性之載波的壓控振盪器就格外重要。 參閱圖1’習知的一種考畢茲（C〇ipitts)振盈器1包 含—轉導值為gni的電晶體Ql、一電感η、一第一電容12 、一第二電容13、一電流源14及一電阻15。該電晶體a 的問極（gate)接收一偏壓Vbias，該電感u及該電阻15在 第電源16及該電晶體Qi的沒極（drain)間並聯，該 弟電谷12跨接在該電晶體（^丨的没極和源極（s〇urce )間 ，該第二電容13的兩端分別電連接到該電晶體Q!的源極及 一第二電源17，該電流源14電連接在該電晶體Ql的源極 與該第二電源17之間。 該考畢兹振盪器1在典型的情況下，需要滿足的振盪 條件為方程式（M)，振盪頻率A為方程式（1_2)，維持穩定 的條件為方程式為（1_3)。 201242237 茗/Λι <<i?15(c12 + c13) 式(l-l) 式 d-2) i cl2+Cl3201242237 VI. Description of the Invention: [Technical Field] The present invention relates to an oscillator, and more particularly to a low power consumption oscillator. [Prior Art] In many high-frequency devices, such as mobile phone wireless transceiver systems, high-frequency measuring instruments or analog digital broadcasting systems, there is a voltage-controlled oscillator to provide a low-frequency original signal to a higher level. The carrier required for high frequency, and the output power, oscillation frequency, modulation range and phase noise of the carrier are related to the demodulation capability of the receiver, so a low power consumption can extend portable mobile products such as mobile phones. A voltage controlled oscillator with a battery life and a carrier that provides the characteristics described above is particularly important. Referring to FIG. 1 'a conventional C〇ipitts vibrator 1 includes a transistor Q1 having a transduction value of gni, an inductor η, a first capacitor 12, a second capacitor 13, and a current Source 14 and a resistor 15. The gate of the transistor a receives a bias voltage Vbias, and the inductor u and the resistor 15 are connected in parallel between the first power source 16 and the drain of the transistor Qi, and the power valley 12 is connected thereto. Between the transistor and the source (s〇urce), the two ends of the second capacitor 13 are electrically connected to the source of the transistor Q! and a second power source 17, respectively. Connected between the source of the transistor Q1 and the second power source 17. In the typical case, the Coppitz oscillator 1 needs to satisfy the oscillation condition of the equation (M), and the oscillation frequency A is the equation (1_2). The condition for maintaining stability is (1_3). 201242237 茗/Λι <<i?15(c12 + c13) Formula (ll) Formula d-2) i cl2+Cl3
Sm =—Si_n+^12.^2 C13^s ci3} 式（1-3) 其中’Ln是該電感u的電感值，Ris是該電阻15的電 阻值，Cu'c!3分別是該第一、第二電容的電容值。當方程 式（1 3)中的C12/C13=l時，g』i5的最小值為4。 。由於轉導值心和功率消耗成正相關，且該種考畢兹振 盈器1所需的穩定振錢件（gAM)的最小值較一般交 錯耦合壓控振盪器所需的穩定振盪條件（认…的最小 值大4倍，所以需要使用更多的電流以及更大的電晶體尺 寸才月b達到所需要的振盪條件，進而大幅降低可攜式無線 通訊產品的待機時間並增加產品體積。 【發明内容] 因此，本發明之目的，即在提供一種低功率消耗的振 盪器。 於疋，本發明振盪器，包含一第一變壓器與一第二變 壓器、一第一電晶體、一第二電晶體、一第三電晶體與一 第四電晶體及兩電容單元。 每一變壓器包括一第一繞組與一第二繞組，每一繞組 包括一第一端及一第二端，每一變壓器的第一與第二繞組 的第二端具有相同的電壓極性。 每一電晶體具有一第一端、一第二端及一控制端。其 201242237 中，該第-與第二變壓器的第一繞组的第一端適用於電連 接到一第一電源，該第一與第三電晶體的第一端分別電連 接到該第一與第二變壓器的第一繞組的第二端，該第二與 第四電晶體的第一端分別電連接到該第一與第三電晶體的 第二端，該第二與第四電晶體的控制端分別電連接到該第 二與第一變壓器的第二繞組的第二端，該第二與第四電晶 體的第二端適用於電連接到一第二電源，該等電容單元在 該第一與第三電晶體的第一端間或第二端間串聯。 本發明之功效即在利用該等變壓器及該第二與第四電 晶體，可以降低該振盪器起始振盪所需之轉導值，而降低 該振盪器的功率損耗。 【實施方式】 有關本發明之前述及其他技術内容、特點與功效，在 以下配合參考圖式之一個較佳實施例的詳細說明中將可 清楚的呈現。 參閱圖2,本發明振盪器之較佳實施例包含一第一變壓 器21、一第二變壓器22、一第一電晶體％、一第二電晶體 M2、一第三電晶體M3 ' —第四電晶體Μ*、兩電容單元23 、一第一電容24及一第二電容25。 該第一變壓器21包括一第一繞組211與一第二繞組 212且每一繞組211、212包括一第一端及一第二端，且該 第與第一繞組211、212的第二端具有相同的電壓極性。 該第二變壓器22包括一第一繞組221與一第二繞組 222，且每一繞組221、222包括一第一端及一第二端，且 201242237 e亥第一與第二繞組221' 222的第二端具有相同的電壓極性 每一電晶體ΜπΜ4具有一第一端、一第二端及一控制 端。在本實施例中，該等電晶體Μι~Μ4是Ν型金屬氧化物 半導體（N-type metal-oxide-semiconductor，NMOS)場效電 b曰體，且第一端是汲極，第二端是源極，控制端是間極。 該第一變壓器21與第二變壓器22的第一繞組211、 22i的第一端適用於電連接到一第一電源26，且該第一電 源26所提供的電壓為ν〇〇，該第一變壓器21與第二變壓器 2的第一繞組212、222的第一端適用於接收一偏壓Gw。 該第與第二電晶體M!、Ms的第一端分別電連接到該第一 八第一變壓器21、22的第一繞組2ιι、22ι的第二端該第 -與第三電晶體Μι、m3的控制端適用於電連接到該第一電 原：6該第一與第四電晶體Μ2、M4的第一端分別電連接 ，該第一與第三電晶體Mi、M3的第二端該第二與第四電 體M2 M4的控制端分別電連接到該第二與第一變壓器 2 21的第一繞組222、212 _第二端，該第二與第四電晶 體m2、m4的第二端適用於電連接到—第二電源27，且該 β電原27所提供的電壓為Vgnd ’小於該第一電源26所 提供的電壓vDD。該第一電容24電連接在該第一電晶體A 的第一端與第二端間’該第二電容25電連接在該第三電晶 體一M3的第-端與第二端間。該等電容單元U纟該第一與 第三電晶體M】、M3的第二端間串聯。該等電容單元23間 /、同接點NA適用於接收一控制電壓，每一電容單 201242237 元23的電容值受該控制電壓影響。 在操作時，該第一及第三電晶體M丨、Μ;的第一端的電 I F。、〆。分別透過該第一及第二變壓器21、22的該等第 一繞組211、221耦合至該等第二繞組212、222，再分別到 達该第四及第二電晶體Μ4、Μζ的控制端，該第四及第二電 晶體Μ*、Μ2再分別將該等控制端的電壓r/、F。-轉換成該 第四及第二電晶體Μ*、M2的該等第一端的一第一電流… 及一第二電流。該第一及第二電流kk分別流經該第 三及該第一電晶體M3、的該等第二端，接著分別流經該 第二及該第一電晶體Μ;、Μι的該等第一端，並分別經由該 第二及第一變壓器22、21的該等第一繞組22ι、2ιι轉換成 電壓以分別增強該第三及該第一電晶體m3、]y^的第一端的 電壓F。、’達到振盪器正回授以增強信號的目的。 參閱圖2與圖3，圖3是圖2振盪器的小訊號等效半電 路模型，且由於該振盪器的電路結構具有對稱性，所以僅 需以一個半電路模型作為說明。 3亥第一繞組221的自感值是以Li來表示，電阻性損耗 疋以電阻值Ri來表示，該第二繞組222的自感值是以^來 表不，電阻性損耗是以電阻值I來表示，該等電晶體Μι、 Μ2的轉導值分別為gmi及，利用小訊號分析可以得到第 電晶體的第一端的電壓匕+對第一電晶體Μι的第二端 的電壓R的轉移函數如方裎式（1_4)及方程式（15)所示當 電路迴路增益為一時，即滿足振盪條件，且此時振盪 頻率Λ可以表示成方程式（1 -6)所示，所以改變該電容單元 £Ζ· 7 201242237 =容值即可控制該振盪器_頻“，且該_ =狀始減該第-電晶體％的轉導值^為方程式（1_ -中振盪胃起始振i時所需 _ =:的轉導一由該第二電晶體％的轉導值二 鐘邀“且由於轉導值〜和功率消耗成正相關，所以降低該 值gw就等同於降低該振盪器的功率消耗。 式（1-4) 式（1-5) 式（1-6) —z(c23+c24)+哭」 SC24 + gm2Sm = -Si_n+^12.^2 C13^s ci3} where (L) is the inductance of the inductor u, Ris is the resistance of the resistor 15, and Cu'c!3 is the first The capacitance value of the second capacitor. When C12/C13=l in the equation (13), the minimum value of g』i5 is 4. . Since the transduction value is positively correlated with the power consumption, and the minimum value of the stable vibration element (gAM) required for the Cobacher oscillator 1 is higher than that required for the general interleaved coupling voltage controlled oscillator (recognition) The minimum value of ... is 4 times larger, so more current and a larger transistor size are required to achieve the required oscillation conditions, thereby greatly reducing the standby time of the portable wireless communication product and increasing the product volume. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a low power consumption oscillator. The oscillator of the present invention includes a first transformer and a second transformer, a first transistor, and a second a crystal, a third transistor and a fourth transistor and two capacitor units. Each transformer includes a first winding and a second winding, each winding including a first end and a second end, each of the transformer The second ends of the first and second windings have the same voltage polarity. Each of the transistors has a first end, a second end, and a control end. In 201242237, the first winding of the first and second transformers The first end is adapted to be electrically connected to a first power source, and the first ends of the first and third transistors are electrically connected to the second ends of the first windings of the first and second transformers, respectively, the second The first ends of the fourth transistor are electrically connected to the second ends of the first and third transistors, respectively, and the control ends of the second and fourth transistors are electrically connected to the second of the second and first transformers, respectively a second end of the winding, the second ends of the second and fourth transistors are adapted to be electrically connected to a second power source, the capacitive units being between the first end or the second end of the first and third transistors The effect of the present invention is that, by using the transformers and the second and fourth transistors, the transduction value required for the initial oscillation of the oscillator can be reduced, and the power loss of the oscillator can be reduced. The foregoing and other technical aspects, features, and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention. Including a first transformer 21, a second change The device 22, a first transistor %, a second transistor M2, a third transistor M3' - a fourth transistor Μ *, two capacitor units 23, a first capacitor 24 and a second capacitor 25. The first transformer 21 includes a first winding 211 and a second winding 212, and each winding 211, 212 includes a first end and a second end, and the second end of the first winding 211, 212 has the same The second transformer 22 includes a first winding 221 and a second winding 222, and each of the windings 221, 222 includes a first end and a second end, and the first and second windings of the 201242237 ehai The second end of 221'222 has the same voltage polarity. Each transistor ΜπΜ4 has a first end, a second end and a control end. In this embodiment, the transistors Μι~Μ4 are Ν-type metal oxide. N-type metal-oxide-semiconductor (NMOS) field-effect electric b-body, and the first end is a drain, the second end is a source, and the control end is a pole. The first ends of the first windings 21 and 22i of the first transformer 21 and the second transformer 22 are adapted to be electrically connected to a first power source 26, and the voltage supplied by the first power source 26 is ν〇〇, the first The first ends of the first windings 212, 222 of the transformer 21 and the second transformer 2 are adapted to receive a bias voltage Gw. The first ends of the first and second transistors M!, Ms are electrically connected to the second ends of the first windings 2, 1 and 22 of the first and eighth first transformers 21, 22, respectively, the first and third transistors, The control end of the m3 is adapted to be electrically connected to the first electric source: 6 the first ends of the first and fourth transistors Μ2, M4 are electrically connected, respectively, and the second ends of the first and third transistors Mi, M3 The control ends of the second and fourth electric bodies M2 to M4 are electrically connected to the first windings 222, 212_the second ends of the second and first transformers 21, respectively, and the second and fourth transistors m2 and m4 The second end is adapted to be electrically connected to the second power source 27, and the voltage supplied by the beta power source 27 is Vgnd' less than the voltage vDD provided by the first power source 26. The first capacitor 24 is electrically connected between the first end and the second end of the first transistor A. The second capacitor 25 is electrically connected between the first end and the second end of the third transistor M3. The capacitor units U are connected in series between the second ends of the first and third transistors M], M3. The capacitors 23 and the same contacts NA are adapted to receive a control voltage, and the capacitance value of each capacitor unit 201242237 yuan 23 is affected by the control voltage. In operation, the first end of the first and third transistors M丨, Μ; Oh. The first windings 211 and 221 respectively passing through the first and second transformers 21 and 22 are coupled to the second windings 212 and 222, and then reach the control ends of the fourth and second transistors Μ4 and Μζ, respectively. The fourth and second transistors Μ* and Μ2 further respectively apply voltages r/, F of the control terminals. Converting to a first current ... and a second current of the first ends of the fourth and second transistors Μ*, M2. The first and second currents kk respectively flow through the second ends of the third and first transistors M3, and then flow through the second and the first transistors Μ; One end is respectively converted into a voltage via the first windings 22ι, 2ιι of the second and first transformers 22, 21 to respectively enhance the first ends of the third and first transistors m3, y^ Voltage F. , 'Achieve the oscillator is being feedback to enhance the signal. Referring to Figures 2 and 3, Figure 3 is a small signal equivalent half-circuit model of the oscillator of Figure 2, and since the circuit structure of the oscillator is symmetrical, only one half-circuit model is required. The self-inductance value of the 3H first winding 221 is represented by Li, the resistive loss 疋 is represented by the resistance value Ri, the self-inductance value of the second winding 222 is represented by ^, and the resistive loss is the resistance value. I indicates that the transconductance values of the transistors Μι and Μ2 are respectively gmi and, by means of small signal analysis, the voltage 第一 at the first end of the first transistor and the voltage R at the second end of the first transistor 可以 can be obtained. The transfer function is as shown in the square equation (1_4) and equation (15). When the gain of the circuit loop is one, the oscillation condition is satisfied, and the oscillation frequency Λ can be expressed as the equation (1 -6), so the capacitance is changed. The unit Ζ· 7 201242237 = the value can control the oscillator _ frequency ", and the _ = shape begins to reduce the transduction value of the first - transistor % ^ is the equation (1_ - in the oscillation of the gastric initial vibration i) The transduction of _ =: is required by the transduction value of the second transistor %, and since the transconductance value is positively correlated with the power consumption, lowering the value gw is equivalent to reducing the power of the oscillator. Consumption. Formula (1-4) Formula (1-5) Formula (1-6) —z(c23+c24)+Cry” SC24 + gm2
^- = ___❽A + 及丨)yC，, 1 (sL，尽 km2畏-ι fd上 ‘ =|(C23 + C24)- gm2 愿& +式(1 ·7) 其中，Cn是該相對應電容單元23的電容值，是該 第一電容24的電容值。 ^ 參閱圖2與圖4,在本實施例中，該等電容單元23可 以疋採用習知的操作在反轉區之變容器，因此，每一電容 單元23包括一第五電晶體Ms，該第五電晶體具有電連 接到該等電容單元23間之該共同接點NA的一第一端與一 第一端、一電連接到該相對應第一電晶體Μ〗或第三電晶體 M3之第二端的控制端，及一適用於電連接到該第二電源27^- = ___❽A + and 丨)yC,, 1 (sL, do km2 fear-ι fd on ' =|(C23 + C24)- gm2 wish & + (1 ·7) where Cn is the corresponding capacitance The capacitance value of the unit 23 is the capacitance value of the first capacitor 24. Referring to FIG. 2 and FIG. 4, in the embodiment, the capacitor units 23 can be variably used in the varistor of the reverse region. Therefore, each of the capacitor units 23 includes a fifth transistor Ms having a first end electrically connected to the common contact NA between the capacitor units 23 and a first end and an electrical connection. a control end to the second end of the corresponding first transistor or third transistor M3, and one adapted to be electrically connected to the second power source 27
S 201242237 的本體端。雖然、操作在反轉區之變容器可以增加電容值的 可調範圍，但卻具有較差的電容品質因素。 參閱圖2與圖5,在本實施例中，該等電容單元23也 可以是採用本申請案的發明人所提出的變容器因此每 一電容單元23除了包括前述的該第五電晶體Ms之外，還 包括一具備高品質因素的金屬·絕緣體-金屬（MIM)電容 51，該等電容單元23的金屬_絕緣體_金屬電容51在該二個 第五電a曰體M5的控制端間串聯，且如圖6所示，圖5的電 容早7L 23相較於圖4的電容單元23的電容品質因素可藉 由該MIM電容51而提升。 曰 參閱表1及表2，是本實施例振盪器採用圖5的電容單 元23以台積電018-μιη Mixed Signal RF CMOS製程技術製 造，再藉由實際量測所得到的驗證值。當該第一電源26的 電壓VDD為ι·35 V時，本實施例振盪器的功率損耗只需3 3 mW，明顯小於參考文獻丨〜6 (均為〇 18cm〇s製程） 的功率消耗。此外，本實施例振盪器的相位雜訊也與該等 參考文獻中具有最佳之相位雜訊的參考文獻2近似，並優 於其他五個參考文獻。 表1 操作頻率 (GHz) 偏移振盪信號 1 MHz的相位 雜訊 (dBc/Hz) 核心功率消耗 (mW) 參考文獻 21.6 -101.75 45 1 201242237 19.9 -111 32 2 21.3 -105.9 9.6 3 19 -110 54 4 24.27 -100.33 7.8 5 21.37 -109.8 3.5 6 18.95 -110.82 3.3 本實施例 表2 晶片面積 (mm2) 效能指數 (dBc/Hz) 效能指數含可 調頻率範圍 (dBc/Hz) 參考文獻 0.544 -171.9 -167.8 1 0.425 -181.9 -170.2 2 0.141 -182.6 -172.2 3 0.806 -178.3 -171.3 4 0.420 -179.1 -166.0 5 0.473 -191.0 -185.1 6 0.239 -191.2 -182.3 本實施例 參閱圖7 ，值得注意的是 ，該等電容單元23也可以在 該第一電晶體Μι的第一端及該第三電晶體M3的第一端間 串聯。 參閱圖8,值得注意的是，該第一電源26所提供的電 壓也可以為VGND，該第二電源27所提供的電壓也可以為 VDD，且該電壓V GND 小於該電壓vDD，該第一至第四電晶 體MclVU是P型金屬氧化物半導體（P-type metal-oxide- s 10 201242237 semiconductor，NMOS)場效電晶體。 綜上所述，本實施例振盪器利用該等變壓器21、22及 該第二與第四電晶體Μ2、M4 ’可以經由該第二及第四電晶 體M2、M4的轉導值gm2、gm4降低該振盪器起振時所需的該 第一及第三電晶體Μ!、M3的轉導值gml、gm3，使該振盪器 具有低的功率消耗、小的晶片面積，並藉由高品質因素的 電容單元23降低相位雜訊，使該振盪器達到優異的效能指 數（Figure-of-Merit，FOM ) ’故確實能達成本發明之目的 〇 惟以上所述者，僅為本發明之較佳實施例而已，當不 能以此限定本發明實施之範圍，即大凡依本發明申請專利 範圍及發明說明内容所作之簡單的等效變化與修飾，皆仍 屬本發明專利涵蓋之範圍内。 參考文獻： 1. D. Ozis，N. Neihart，and D. Allstot，“Differential VCO and passive frequency doubler in 0.18-um CMOS for 24 GHz applications,5, in IEEE RFIC Symp., pp. 36-39, 2006. 2. Η. H. Hsieh and L. H. Lu, 4tA low-phase-noise K-band CMOS ν〇0,?, IEEE Microw. and Wireless Comport. Lett., vol. 16, no. 10, pp. 552-554, Oct. 2006. 3. C. C. Li, T. P. Wang, C. C. Kuo, M. C. Chuang, and H. Wang, “A 21-GHz complementary transformer-coupled CMOS VCO55, IEEE Microw. and Wireless Comport. Lett., 11 201242237 vol. 16, pp.278-280, April 2008. 4. Y. H. Chen, Η. H. Hsieh, and L. H. Lu, tlA 24-GHz receiver frontend with an LO Signal Generator in 0.18- um CMOS,55 IEEE Trans. Microw. Theory Tech., vol. 56, no. 5, pp. 1043-1051, May 2008. 5. J. Yang, C· Y. Kim, D· W. Kim, and S. Hong, “Design of a 24-GHz CMOS VCO with an asymmetric-width transformer,” IEEE Trans. Circuit and Systems Part-II Express Briefs, vol. 57, no. 3, pp. 173-177, March 2010. 6. S. L. Liu, K. H. Chen, T. Chang, and A. Chin, UA low-power K-band CMOS VCO with four-coil transformer feedback,5, IEEE Microw. and Wireless Comport. Lett., vol. 20, pp.459-461, Aug. 2010. 【圖式簡單說明】 圖1是一種習知的考畢茲振盪器的電路圖； 圖2是本發明振盪器的一較佳實施例的電路圖，說明 第一至第四電晶體是N型電晶體，兩電容單元在該第一電 晶體的第二端及該第三電晶體的第二端間串聯， 圖3是該較佳實施例的小訊號等效半電路模型； 圖4是該等電容單元的一種實施態樣的電路圖； 圖5是該等電容單元的另一種實施態樣的電路圖； 圖6是圖4的電容單元與圖5的電容單元的電容品質 因素的比較圖； 圖7是該較佳實施例的一種變形的電路圖，說明該等The body side of S 201242237. Although the varactor operating in the reversal zone can increase the adjustable range of capacitance values, it has a poor capacitance quality factor. Referring to FIG. 2 and FIG. 5, in the embodiment, the capacitor units 23 may also be varactors proposed by the inventors of the present application. Therefore, each capacitor unit 23 includes the fifth transistor Ms described above. In addition, a metal-insulator-metal (MIM) capacitor 51 having high quality factors is included, and the metal_insulator-metal capacitor 51 of the capacitor unit 23 is connected in series between the control terminals of the two fifth electric a-body M5. As shown in FIG. 6, the capacitance of the capacitor of FIG. 5 7L 23 is higher than that of the capacitor unit 23 of FIG. 4 by the MIM capacitor 51.参阅 Referring to Table 1 and Table 2, the oscillator of this embodiment is fabricated by using the capacitor unit 23 of FIG. 5 by a TSMC 018-μιη Mixed Signal RF CMOS process technology, and then obtained by actual measurement. When the voltage VDD of the first power source 26 is ι·35 V, the power loss of the oscillator of this embodiment is only 3 3 mW, which is significantly smaller than the power consumption of the reference 丨~6 (both 〇 18 cm 〇s process). Furthermore, the phase noise of the oscillator of this embodiment is similar to that of reference 2 having the best phase noise in the references, and is superior to the other five references. Table 1 Operating frequency (GHz) Offset oscillation signal 1 MHz phase noise (dBc/Hz) Core power consumption (mW) References 21.6 - 101.75 45 1 201242237 19.9 -111 32 2 21.3 -105.9 9.6 3 19 -110 54 4 24.27 -100.33 7.8 5 21.37 -109.8 3.5 6 18.95 -110.82 3.3 Table 2 wafer area (mm2) Effectiveness index (dBc/Hz) Performance index with adjustable frequency range (dBc/Hz) Reference 0.544 -171.9 - 167.8 1 0.425 -181.9 -170.2 2 0.141 -182.6 -172.2 3 0.806 -178.3 -171.3 4 0.420 -179.1 -166.0 5 0.473 -191.0 -185.1 6 0.239 -191.2 -182.3 This embodiment refers to Figure 7, it is worth noting that The equal capacitance unit 23 may also be connected in series between the first end of the first transistor 及 and the first end of the third transistor M3. Referring to FIG. 8, it is noted that the voltage provided by the first power source 26 may also be VGND, the voltage provided by the second power source 27 may also be VDD, and the voltage V GND is less than the voltage vDD, the first The fourth transistor MclVU is a P-type metal-oxide-s 10 201242237 semiconductor (NMOS) field effect transistor. In summary, the oscillator of the embodiment utilizes the transformers 21, 22 and the second and fourth transistors Μ2, M4' can pass the transconductance values gm2, gm4 of the second and fourth transistors M2, M4. Reducing the transconductance values gml, gm3 of the first and third transistors Μ!, M3 required for the oscillator to start, so that the oscillator has low power consumption, small wafer area, and high quality The capacitive unit 23 of the factor reduces the phase noise, so that the oscillator achieves an excellent performance index (Figure-of-Merit, FOM), so it is indeed possible to achieve the object of the present invention, which is only the above. The present invention is not limited by the scope of the invention, and the simple equivalent changes and modifications made by the invention in the scope of the invention and the scope of the invention are still within the scope of the invention. References: 1. D. Ozis, N. Neihart, and D. Allstot, "Differential VCO and passive frequency doubler in 0.18-um CMOS for 24 GHz applications, 5, in IEEE RFIC Symp., pp. 36-39, 2006 2. H. Hsieh and LH Lu, 4tA low-phase-noise K-band CMOS ν〇0,?, IEEE Microw. and Wireless Comport. Lett., vol. 16, no. 10, pp. 552- 554, Oct. 2006. 3. CC Li, TP Wang, CC Kuo, MC Chuang, and H. Wang, “A 21-GHz complementary transformer-coupled CMOS VCO55, IEEE Microw. and Wireless Comport. Lett., 11 201242237 vol 16, pp.278-280, April 2008. 4. YH Chen, Η. H. Hsieh, and LH Lu, tlA 24-GHz receiver frontend with an LO Signal Generator in 0.18-um CMOS, 55 IEEE Trans. Microw. Theory Tech., vol. 56, no. 5, pp. 1043-1051, May 2008. 5. J. Yang, C. Y. Kim, D. W. Kim, and S. Hong, “Design of a 24- GHz CMOS VCO with an asymmetric-width transformer,” IEEE Trans. Circuit and Systems Part-II Express Briefs, vol. 57, no. 3, pp. 173-177, March 2010. 6. SL Liu, KH Chen, T. Chang , and A. Chin, UA low-power K-band CMOS VCO with four-coil transformer feedback, 5, IEEE Microw. and Wireless Comport. Lett., vol. 20, pp. 459-461, Aug. 2010. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a conventional Colpitts oscillator; FIG. 2 is a circuit diagram of a preferred embodiment of the oscillator of the present invention, illustrating that the first to fourth transistors are N-type transistors, two The capacitor unit is connected in series between the second end of the first transistor and the second end of the third transistor. FIG. 3 is a small signal equivalent half circuit model of the preferred embodiment; FIG. 4 is a capacitor unit of the capacitor unit. FIG. 5 is a circuit diagram of another embodiment of the capacitor unit; FIG. 6 is a comparison diagram of capacitance factors of the capacitor unit of FIG. 4 and the capacitor unit of FIG. 5; FIG. A modified circuit diagram of a preferred embodiment illustrating these
S 12 201242237 電容單元在該第一電晶體的第一端及該第三電晶體的第一 端間串聯；及 圖8是該較佳實施例的另一種變形的電路圖，說明第 一至第四電晶體是P型電晶體。 13 3 201242237 【主要元件符號說明】 1…… …考畢茲振盪器 221 …· …第一繞組 11 •… …電感 222 .... …第一繞組 12 •… …第一電容 23....... …電容單元 13 ·. …第二電容 24....... …第一電容 14..... …電流源 25....... …第二電容 15 ••… …電阻 26....... …第 電源 16 •.… …第一電源 27....... …第二電源 17 ••… …第一電源 M5 ··.·· …第五電晶體 Q.…·· •…電晶體 51…… …金屬-絕緣體-金屬 M,…· •…第一電晶體 電容 M2 ..... …·第二電晶體 NA·.··. …共同接點 M3 ··.. •…第三電晶體 V DD …電壓 M4… …·第四電晶體 VGND *' ···電壓 21…… •…第一變壓器 Vctr丨… …控制電壓 211… •…第一繞組 Vb i as …偏壓 212… •…第二繞組 22••… •…第二變壓器S 12 201242237 The capacitor unit is connected in series between the first end of the first transistor and the first end of the third transistor; and FIG. 8 is a circuit diagram showing another variation of the preferred embodiment, illustrating first to fourth The transistor is a P-type transistor. 13 3 201242237 [Explanation of main component symbols] 1...... ...Kobitz oscillator 221 ...·...first winding 11 •...inductor 222 .......first winding 12 •...first capacitor 23... .... ...capacitor unit 13 ·....second capacitor 24....first capacitor 14.....current source 25....the second capacitor 15 •• ...resistance 26.......the first power supply 16 •....the first power supply 27.........the second power supply 17 ••...the first power supply M5 ····· ... Five transistors Q....··•...transistor 51......metal-insulator-metal M,...·......first transistor capacitor M2 ........·second transistor NA·.··. ...common contact M3 ··.. •...third transistor V DD ...voltage M4...the fourth transistor VGND *' ···voltage 21... •...first transformer Vctr丨...control voltage 211... •...first winding Vb i as ...bias 212... •...second winding 22••... •...second transformer
S 14S 14