【正文】 生躍變，相應(yīng)輸出高電平或低電平。圖6－1所示為一最簡單的電壓比較器，UR為參考電壓，加在運放的同相輸入端，輸入電壓ui加在反相輸入端。輸出端電位被其箝位在穩(wěn)壓管的穩(wěn)定電壓UZ，即uO＝UZ 當(dāng)ui＞UR時，運放輸出低電平，DZ正向?qū)?，輸出電壓等于穩(wěn)壓管的正向壓降UD，即uo＝－UD 因此，以UR為界，當(dāng)輸入電壓ui變化時，輸出端反映出兩種狀態(tài)：高電位和低電位。 圖6－1(b)為(a)圖比較器的傳輸特性。過零比較器電路如圖6－2所示為加限幅電路的過零比較器，DZ為限幅穩(wěn)壓管。當(dāng)Ui＞0時，輸出UO＝(UZ+UD)，當(dāng)Ui＜0時，UO＝+(UZ+UD)。過零比較器結(jié)構(gòu)簡單，靈敏度高，但抗干擾能力差。過零比較器在實際工作時，如果ui恰好在過零值附近，則由于零點漂移的存在，uO將不斷由一個極限值轉(zhuǎn)換到另一個極限值，這在控制系統(tǒng)中，對執(zhí)行機構(gòu)將是很不利的。如圖6－3所示，從輸出端引一個電阻分壓正反饋支路到同相輸入端，若uo改變狀態(tài)，∑點也隨著改變電位，使過零點離開原來位置。故只有當(dāng)ui下降到－U∑以下，才能使uO再度回升到U+，于是出現(xiàn)圖63(b)中所示的滯回特性。改變 R2的數(shù)值可以改變回差的大小。如＜Ui＜，窗口比較器的輸出電壓UO等于運放的正飽和輸出電壓(+Uomax)，如果Ui＜或Ui＞，則輸出電壓U0等于運放的負(fù)飽和輸出電壓(－UOmax)。整理實驗數(shù)據(jù)，繪制各類比較器的傳輸特性曲線 　總結(jié)幾種比較器的特點，闡明它們的應(yīng)用。(1) 接通177。 (2) 測量ui懸空時的UO值。(4) 改變ui幅值，測量傳輸特性曲線。 (1) 按圖接線，ui接＋5V可調(diào)直流電源，測出uO由＋Uomcx→－Uomcx時ui的臨界值。(3) ui接500Hz，峰值為2V的正弦信號，觀察并記錄 ui→uO波形。圖6－5 反相滯回比較器 同相滯回比較器實驗線路如圖6－6所示(1) 參照2，自擬實驗步驟及方法。圖6－6 同相滯回比較器 窗口比較器 參照圖64自擬實驗步驟和方法測定其傳輸特性。若要將圖64窗口比較器的電壓傳輸曲線高、低電平對調(diào)，應(yīng)如何改動比較器電路。二、實驗原理　　從結(jié)構(gòu)上看，正弦波振蕩器是沒有輸入信號的，帶選頻網(wǎng)絡(luò)的正反饋放大器。 RC移相振蕩器電路型式如圖7－1所示,選擇R＞＞Ri。 頻率范圍 　 幾赫～數(shù)十千赫。 振蕩頻率 起振條件 ||＞3電路特點 可方便地連續(xù)改變振蕩頻率，便于加負(fù)反饋穩(wěn)幅，容易得到良好的振蕩波形。圖7－3 雙T選頻網(wǎng)絡(luò)振蕩器原理圖振蕩頻率 起振條件 ||＞1電路特點 選頻特性好，調(diào)頻困難，適于產(chǎn)生單一頻率的振蕩。 三、實驗內(nèi)容 　RC串并聯(lián)選頻網(wǎng)絡(luò)振蕩器（1）按圖7－4組接線路。UB1（V）UC1（V）UE1（V）UB2（V）UC2（V）UE2（V）Ui（V）UO（V）AV (3) 接通RC串并聯(lián)網(wǎng)絡(luò)，調(diào)節(jié)電位器Rf使電路起振，用示波器觀測輸出電壓uO波形，調(diào)節(jié)Rf使獲得滿意的正弦信號，記錄波形幅值。T計算 = f計算 = T測量 = f測量 = (5) 改變R或C值，觀察振蕩頻率變化情況。且輸入、輸出同相位，此時信號源頻率為 F（Hz）10100200500800900950980990995100011001200V0 雙T選頻網(wǎng)絡(luò)振蕩器(1) 按圖10－5組接線路 (2) 斷開雙T網(wǎng)絡(luò)，調(diào)試T1管靜態(tài)工作點，使UC1為6～7V。若不起振，調(diào)節(jié)RW1，使電路起振。圖7－5 雙T網(wǎng)絡(luò)RC正弦波振蕩器 * RC移相式振蕩器的組裝與調(diào)試(1) 按圖7－6組接線路。 (3) 接通RC移相電路，調(diào)節(jié)RB2使電路起振，并使輸出波形幅度最大，用示波器觀測輸出電壓uO波形，同時用頻率計和示波器測量振蕩頻率，并與理論值比較。圖7－6 RC移相式振蕩器 四、預(yù)習(xí)要求 　復(fù)習(xí)教材有關(guān)三種類型RC振蕩器的結(jié)構(gòu)與工作原理。 　如何用示波器來測量振蕩電路的振蕩頻率。 總結(jié)三類RC振蕩器的特點。二、評分標(biāo)準(zhǔn)實驗考試滿分100分，其中動手操作部分由教師當(dāng)堂查看、驗收電路，進(jìn)行數(shù)據(jù)認(rèn)可。 to implement , do not want to, dare not, not with disciplinary ruler to supervision。 not to have conquered, but to have fought well. 2, the plain is the background of life. Live a plain life, give up on themselves is not a coward, but the wise answers。 not unrewarding perfunctorily, but calm attitude of life of unrestrained selfconfidence. Plain living, there is no noise noisy, no earthly troubles, more did not fill in the discontent of desire, some just a calm, a calm. 3, memory of heart will not good things to erase the, life is a When no movie, pain is a beginning, the struggle is a kind of process, death is a kind of ending. Give up this giving up is the helpless, do not give up the abandoned, do not give up this giving up is ignorance, do not give up should not give up is persistent. 4, a thing figured is heaven, think impassability is hell. Since the living, to live better. Sometimes we because of too narrowminded, too care around the chores and penny wise and pound foolish, not worth the candle. Some things to attract trouble and worry, pletely depends on how we look at and deal with it. Don39。t get into a blind alley, don39。t be narrowminded. Poke to care, is a kind of openminded, a free and easy. 5, I am not afraid of others behind me a knife, I afraid to look back and see stab me, is my intention to treat people。m afraid he turned to it as a joke to tell don39。 and when we are in a negative state of mind, you will find many depressed things。 loss of sink, Eritrea pany. When you are in adversity, may wish to change a point of view to think everything over to the good Think, because good mentality decided the fate of the! 7, people are tired, rest。 you pain, no one can understand. Then you only tears to smile. 8, each people have youth,Each youth are a story, the life of the world never gets easier, I want what, wish the world all know, as has been the same。s mouth, because words will reduce its importance。t envy who. Like a person is a kind of feeling, not like a person is true. The truth is easy to explain, I feel Is unspeakable. The best travel life is that you in a strange place found a long lost touched. 11, happy life not in the bustling in, and in the peace of mind。am, like a movie, learn to appreciate, learn to be grateful, learn tolerance, and goodness, helping others. Instead of accusing the society, as into one。t envy him A sum of, don39。t let everyone like you, so also do not want to do. Life is too short to go crazy to love to go to waste, to chase the dream to regret. 15, when temper, a blessing to go. A wounding elegant people, the key is to control their own emotions. With the mouth is the most stupid behavior. A control negative emotions than a can take a city more powerful water flow slow, language is expensive. People spent two years of time to learn to speak, but to spend a few years time to shut up. That is a kind of ability, that is a kind of wisdom. 16, life is not perfect, sometimes, growth is not a cry, not an eyeful of tears, there is no trace of emotion, there is no gleam of hope, no desire, no action, no static, there is only one kind of downward sinking feeling, sink A murky? 6? 7? 6? 7 sink? 6? 7? 6? 7 toward the bottom of the sink. 17, in some way, do not go, you will not know the other side scenery is beautiful. To you is not good, you do not mind too much, no one has an obligation to you。 how do you treat people, does not represent how others treat you, if cannot see through this point, only inviting worry. 18, time is like a sponge in the water, as long as you are willing to squeeze, the total water is still there. Every life, after the ups and downs The best test of live, to life, survival and continuation, do not stop the struggle in the joys and sorrows of life on the road, so that different soul to bear life beat, acceptance of suffering. 19, indifferent to heart, calmly in table, elegan