晶體(ti)諧(xie)振器的等效電(dian)路(lu)

石(shi)英(ying)晶(jing)(jing)體諧振(zhen)(zhen)器(qi)的(de)(de)等效(xiao)(xiao)電(dian)路(lu)。當晶(jing)(jing)體不振(zhen)(zhen)動時(shi)，可(ke)把它(ta)看成(cheng)一個(ge)平板(ban)電(dian)容(rong)器(qi)稱為靜(jing)電(dian)電(dian)容(rong)C，它(ta)的(de)(de)大(da)(da)小與(yu)晶(jing)(jing)片(pian)(pian)的(de)(de)幾何(he)尺(chi)(chi)寸(cun)、電(dian)極(ji)面積有(you)(you)(you)關，一般(ban)約(yue)幾個(ge)PF到(dao)幾十PF。當晶(jing)(jing)體振(zhen)(zhen)蕩時(shi)，差分晶(jing)(jing)振(zhen)(zhen)現貨(huo)，機械振(zhen)(zhen)動的(de)(de)慣性可(ke)用(yong)電(dian)感L來等效(xiao)(xiao)。一般(ban)L的(de)(de)值為幾十mH到(dao)幾百mH。晶(jing)(jing)片(pian)(pian)的(de)(de)彈(dan)性可(ke)用(yong)電(dian)容(rong)C來等效(xiao)(xiao)，差分晶(jing)(jing)振(zhen)(zhen)，C的(de)(de)值很(hen)小，一般(ban)只(zhi)有(you)(you)(you)0.00020.1pF。晶(jing)(jing)片(pian)(pian)振(zhen)(zhen)動時(shi)因(yin)摩擦(ca)而(er)造成(cheng)的(de)(de)損耗(hao)用(yong)R來等效(xiao)(xiao)，它(ta)的(de)(de)數(shu)值約(yue)為100Ω。由于晶(jing)(jing)片(pian)(pian)的(de)(de)等效(xiao)(xiao)電(dian)感很(hen)大(da)(da)，而(er)C很(hen)小，R也小，因(yin)此(ci)回路(lu)的(de)(de)品質因(yin)數(shu)Q很(hen)大(da)(da)，可(ke)達1000～10000。加上晶(jing)(jing)片(pian)(pian)本(ben)身的(de)(de)諧振(zhen)(zhen)頻率基本(ben)上只(zhi)與(yu)晶(jing)(jing)片(pian)(pian)的(de)(de)切割方式、幾何(he)形狀、尺(chi)(chi)寸(cun)有(you)(you)(you)關，而(er)且可(ke)以做(zuo)得準確，因(yin)此(ci)利用(yong)石(shi)英(ying)諧振(zhen)(zhen)器(qi)組(zu)成(cheng)的(de)(de)振(zhen)(zhen)蕩電(dian)路(lu)可(ke)獲得很(hen)高的(de)(de)頻率穩定度。

晶(jing)體(ti)振蕩器有(you)哪些應用？

晶體振蕩器廣泛(fan)用于系統頻(pin)率源、導航(hang)以及其它通(tong)訊領(ling)域的(de)普通(tong)石英(ying)晶體振蕩器(PXO)，工作(zuo)頻(pin)率范圍在1MHz至150MHz之間(jian)，頻(pin)率穩定度為±25ppm，±50ppm和±100ppm，輸出上升和下降時間(jian)為5ns，老化率為±5ppm/年。

還有(you)(you)主要(yao)用于(yu)移動電(dian)話、筆記本電(dian)腦、PHS、GPS設(she)備和(he)其它無線通信(xin)設(she)備的(de)SMD晶(jing)(jing)(jing)體振蕩器(PXO)和(he)SMD壓(ya)控/溫補(bu)晶(jing)(jing)(jing)體振蕩器(VCXO/TCXO/VCTCXO)，其PXO和(he)VCXO型SMD晶(jing)(jing)(jing)振輸出邏輯與(yu)HCMOS/TTL兼容(rong)，因而提高(gao)(gao)了(le)器件(jian)的(de)適應性(xing)和(he)設(she)計的(de)靈活(huo)性(xing)。用于(yu)手(shou)機(ji)的(de)SMD晶(jing)(jing)(jing)振主要(yao)特點(dian)有(you)(you)高(gao)(gao)精度、高(gao)(gao)穩(wen)定度和(he)小尺寸(cun)，精度高(gao)(gao)達±5ppm，同時(shi)采用的(de)晶(jing)(jing)(jing)片(pian)色澤白皙同時(shi)具(ju)有(you)(you)低腐蝕性(xing)、不(bu)易起振，質量很穩(wen)定，尺寸(cun)規(gui)格(ge)有(you)(you)7×5mm、6×3.5mm、5×3.2mm、4×2.5mm。

頻率(lv)標準(zhun)、通訊、電子儀表、測試裝置(zhi)、精密計量等領域(yu)的高(gao)精度高(gao)穩(wen)定度石英晶體振(zhen)(zhen)蕩器，可根據長期頻率(lv)穩(wen)定度不同分為TCXO、OCXO、VCXO、SPXO、LPXO(低噪聲(sheng)晶體振(zhen)(zhen)蕩器)等類型(xing)。

石(shi)英晶體振蕩器(qi)的(de)應用

石(shi)(shi)英(ying)(ying)鐘(zhong)走(zou)(zou)(zou)時(shi)(shi)(shi)(shi)準(zhun)、耗電(dian)(dian)(dian)(dian)(dian)省為其優點。不論是(shi)老式石(shi)(shi)英(ying)(ying)鐘(zhong)或是(shi)新(xin)式多功(gong)能石(shi)(shi)英(ying)(ying)鐘(zhong)都(dou)是(shi)以(yi)(yi)石(shi)(shi)英(ying)(ying)晶(jing)(jing)體振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)器(qi)(qi)為電(dian)(dian)(dian)(dian)(dian)路(lu)，差(cha)分晶(jing)(jing)振(zhen)(zhen)(zhen)生(sheng)產廠家，其頻(pin)率精(jing)度(du)(du)決定了(le)電(dian)(dian)(dian)(dian)(dian)子鐘(zhong)表的(de)(de)走(zou)(zou)(zou)時(shi)(shi)(shi)(shi)精(jing)度(du)(du)。石(shi)(shi)英(ying)(ying)晶(jing)(jing)體振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)器(qi)(qi)原理的(de)(de)示(shi)(shi)意(yi)如圖3所(suo)(suo)示(shi)(shi)，差(cha)分晶(jing)(jing)振(zhen)(zhen)(zhen)原廠，其中(zhong)V1和(he)V2構(gou)成(cheng)CMOS反相器(qi)(qi)石(shi)(shi)英(ying)(ying)晶(jing)(jing)體Q與(yu)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)電(dian)(dian)(dian)(dian)(dian)容(rong)C1及(ji)微調(diao)電(dian)(dian)(dian)(dian)(dian)容(rong)C2構(gou)成(cheng)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)系統(tong)(tong)，這里石(shi)(shi)英(ying)(ying)晶(jing)(jing)體相當于(yu)電(dian)(dian)(dian)(dian)(dian)感。振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)系統(tong)(tong)的(de)(de)元件參數(shu)確定了(le)振(zhen)(zhen)(zhen)頻(pin)率。一(yi)般Q、C1及(ji)C2均為外接(jie)元件。另外R1為反饋電(dian)(dian)(dian)(dian)(dian)阻，R2為振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)的(de)(de)穩定電(dian)(dian)(dian)(dian)(dian)阻，它們都(dou)集成(cheng)在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)路(lu)內(nei)部。故無法通過改(gai)變C1或C2的(de)(de)數(shu)值(zhi)來調(diao)整(zheng)走(zou)(zou)(zou)時(shi)(shi)(shi)(shi)精(jing)度(du)(du)。但此時(shi)(shi)(shi)(shi)仍可用(yong)加接(jie)一(yi)只(zhi)電(dian)(dian)(dian)(dian)(dian)容(rong)C有方法，來改(gai)變振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)系統(tong)(tong)參數(shu)，以(yi)(yi)調(diao)整(zheng)走(zou)(zou)(zou)時(shi)(shi)(shi)(shi)精(jing)度(du)(du)。根據電(dian)(dian)(dian)(dian)(dian)子鐘(zhong)表走(zou)(zou)(zou)時(shi)(shi)(shi)(shi)的(de)(de)快慢(man)，調(diao)整(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)有兩種接(jie)法:若走(zou)(zou)(zou)時(shi)(shi)(shi)(shi)偏快，則(ze)可在(zai)(zai)石(shi)(shi)英(ying)(ying)晶(jing)(jing)體兩端并(bing)接(jie)電(dian)(dian)(dian)(dian)(dian)容(rong)C，如圖4所(suo)(suo)示(shi)(shi)。此時(shi)(shi)(shi)(shi)系統(tong)(tong)總(zong)(zong)電(dian)(dian)(dian)(dian)(dian)容(rong)加大，振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)頻(pin)率變低(di)，走(zou)(zou)(zou)時(shi)(shi)(shi)(shi)減慢(man)。若走(zou)(zou)(zou)時(shi)(shi)(shi)(shi)偏慢(man)，則(ze)可在(zai)(zai)晶(jing)(jing)體支路(lu)中(zhong)串接(jie)電(dian)(dian)(dian)(dian)(dian)容(rong)C。如圖5所(suo)(suo)示(shi)(shi)。此時(shi)(shi)(shi)(shi)系統(tong)(tong)的(de)(de)總(zong)(zong)電(dian)(dian)(dian)(dian)(dian)容(rong)減小，振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)頻(pin)率變高，走(zou)(zou)(zou)時(shi)(shi)(shi)(shi)增快。只(zhi)要經過耐心的(de)(de)反復試驗(yan)，就(jiu)可以(yi)(yi)調(diao)整(zheng)走(zou)(zou)(zou)時(shi)(shi)(shi)(shi)精(jing)度(du)(du)。因此，晶(jing)(jing)振(zhen)(zhen)(zhen)可用(yong)于(yu)時(shi)(shi)(shi)(shi)鐘(zhong)信號(hao)發生(sheng)器(qi)(qi)。