模擬設計的100條圣經 1、Capacitors and resistors have parasitic inductance, about 0.4nH for surface mount and 4nH for a leaded component. 電阻跟電容都有寄生電感，貼片封裝的大概0.4nH，插件的大概4nH。 2、Capacitors and resistors have parasitic inductance, about 0.4nH for surface mount and 4nH for a leaded component. 如果你不想通過在高帶寬晶體管三個引腳中的至少兩個引腳放置損耗元件的方法消除振蕩.鐵氧體磁珠會起到很好的作用. 3、When taking DC measurements in a circuit and they don"t make sense, suspect that something is oscillating. 對一個電路采用直流測試并且不起作用時,應該懷疑有元件在振蕩 4、Opamps will often oscillate when driving capacitive loads. 運放在驅動容性負載時經常會震蕩。 5、The baseemitter voltage Vbe of a small signal transistor is about 0.65v and drops about 2mV/deg C. Vbe goes down with increasing temp. 小信號晶體管的基-射極電壓Vbe大約是0.65伏特，大約以2毫伏/攝氏度的速度降低。Vbe隨著溫度的升高而降低。 6、Multiply 0.13nV by the square root of the ohmic value of a resistor to find the noise in a 1Hz bandwidth. Then multiply by the square root of the BW in Hz gives the total noise voltage. 電阻阻值的平方根，乘以0.13納伏，可以得到1赫茲帶寬的噪聲。再乘以以赫茲為單位的帶寬的平方根，可以得到總噪聲電壓。 7、Johnson noise current goes down with a increase in resistance. Johnson噪聲電流隨著電阻的增加而降低. 8、The impedance looking into the emitter of a transistor at room temp is 26Ohm/Ie in mA 室溫下晶體管射極阻抗為26歐姆/mA 9、All amplifiers are differential in that they are referenced to ground somewhere. 所有的放大器都是相對于某個地電平的差分放大。 10、Typical metal film resistor has a temp coef of about 100 ppm/deg C （典型的金屬薄膜電阻具備100 ppm/deg C的溫度系數） 11、The input noise voltage of a quiet op amp is 1nv/sqrt(Hz) but there are plenty available with 20nV/sqrt(Hz). Op amps with bipolar front-ends have lower voltage noise and higher current noise than those with FET front-ends （低噪音運放的輸入噪聲電壓可以達到1nv/sqrt(Hz) ，但是我們大量用到的運放具有20nV/sqrt(Hz)的輸入噪音。雙極晶體管結構比FET結構的運算放大器具備更地的電壓噪聲和更高的電流噪聲） 12、Using an LC circuit as a power supply filter can actually multiply the power supply noise at the filter"s resonant frequency. Use inductor with low Q to overcome this. （用LC濾波器對電源濾波將會增加電源在濾波器諧振頻率點上的噪聲，通過選擇低Q的電感可以有效克服這一點。） 13、Use comparators for comparing and op amps for amplifying and don"t even think of mixing the two. （用比較器進行比較，用運放進行放大，千萬不要搞混。） 14、Ceramic caps with any other dielectric other than NPO should only be used for bypass applications. （ 除高頻瓷片電容外的瓷片電容僅可用作旁路電容） 15、An N-channel enhancement-mode FET needs +ve voltage on the gate-source to conduct form drain-source. n溝道增強型mosfet需要在gate-source 間接入正電壓來控制drain-source間的電流Ids 16、Small signal JFETS work very well as low-leakage diodes by connecting drain & source together in log current-to-voltage converters and low leakage input protection. Small signal bipolars with b-c tied together will also make nice low-leakage diodes. JFETS短接源漏極在小信號電流-電壓轉換和輸入保護方面具備和低泄漏二極管媲美的特性，小信號測量中晶體管B-E極短接也相當于一個優異的低泄漏二極管。 17、With low pass filter use Bessel for least amount of overshoot in the time domain, and Cauer (or elliptic) for fastest rolloff in the freq domain. 設計低通濾波器時選用貝塞爾型可以使時域較平坦，沒有太多過沖，選用切比雪夫可以提高截止頻率的陡峭性。 18、dB is always 10 times the log of the ratio of 2 powers. 分貝是10*lg的比值。 19、At low frequencies, the current in the collector of a transistor is in phase with the applied current at the base. At high frequencies the current at the collector lags by 90deg. You must appreciate this simple fact to understand high frequency oscillators. 低頻情況下，晶體管集電極電流與基極電流同相，但在高頻情況下，集電極電流相位上滯后90度，這有助于你理解高頻振蕩。 20、The most common glass-epoxy PCB material (FR4) has a dielectric constant of about 4.3 To make a trace with a characteristic impedance of 100 Ohm, use a trace thickness of about 0.4 times the thickness of the board with a ground plane on the opposite side. For a 50Ohm trace make it 2 times the thickness. PCB應用最普通的FR4材料的介質常數大約為4.3，印制版線為得到100歐的特征阻抗需要的線寬為PCB板（背面覆銅）厚度的0.4倍，50歐的阻抗需要線寬為板后的2倍。--線長呢？不解 21、If you need a programmable dynamic current source, find out about operational transconductance amps. Most of the problem is figuring out when you need a programmable dynamic current source. 當你用跨導運算放大器作為可編程動態電流源時你會發現很多問題。 22、A CMOS output with an emitter follower can drive a 5V relay nicely as the relays normally have a must-make spec of 3.5V. This saves power and require no flyback components. CMOS輸出配合一個射極跟隨器可以很好的驅動一個5V工作的繼電器（必須是3.5V以上才能正常工作），這樣節省了功率并不需要反饋元件。 23、Typical thermocouple potential is 30uV/degC. Route signals differentially, along the same path, avoid temp gradients. DPDT latching relays won"t heat up when multiplexing these signals. 典型的熱電偶電位是 30uV/degC，布線是差分信號要盡量走同樣的路徑避免差分線上產生溫度梯度。當需要切換這些信號時，雙刀雙擲常閉繼電器可以避免切換過程中產生的熱量，影響熱電偶溫度測量的精度。 24、You SHOULD be bothered by a design that looks messy, cluttered or indirect. This uncomfortable feeling is one of the few indications that there"s a better way. 你可能會直接或間接的感到設計的電路感混亂不堪，這種不好的感覺其實是一種很寶貴的暗示，那就是那肯定還有一直能夠更好的設計路徑