模拟设计中的100条经验—中文翻译(二校版)

1/ Capacitors and resistors have parasitic inductance, about 0.4nH for surface mount and 4nH for a leaded component.

表贴阻容元件有0.4nH的寄生电感，而直插阻容元件有4nH的寄生电感。

2/ If you don"t want a high bandwidth transistor to oscillate place lossy components in at least 2 of the 3 leads. Ferrite beads work well.

为避免高频晶体管震荡，需在三个引脚中的至少两个上放置损耗元件，例如磁珠。（2013/6/13）

3/ When taking DC measurements in a circuit and they don"t make sense, suspect that something is oscillating.

若测不出电路中的直流量，可能某个元件引起了振荡。

4/ Op-amps will often oscillate when driving capacitive loads.

驱动容性负载时运放容易振荡。

5/ The base-emitter voltage Vbe of a small signal transistor is about 0.65v and drops about 2mV/deg C. Vbe goes down with increasing temp.

小信号晶体管的基射极压降Vbe约为0.65v，温度每升高1摄氏度Vbe下降2mV（负温度系数）。

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.

0.13nV乘以电阻值的平方根得到每赫兹带宽上的噪声，再乘上以频率为单位的带宽的平方根得到总的噪声电压。（2013/6/13）

7/ Johnson noise current goes down with a increase in resistance.

约翰逊噪声电流（热噪声）随电阻的增加而减小。

8/ The impedance looking into the emitter of a transistor at room temp is 26Ohm/Ie in mA

室温下晶体管发射极阻抗与射极电流的关系为26ohm/mA 。

9/ All amplifiers are differential in that they are referenced to ground somewhere.

所有放大器的特性参数因其参考地的不同而有所差别。

10/ Typical metal film resistor has a temp coef of about 100 ppm/deg C

典型金属膜电阻的温度系数是100 ppm/℃。

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

虽然低噪运放的输入噪声电压是1 nV / √Hz但是很多应用是在20nV/ √Hz 。相比于场效应管型前端放大电路，双极型前端放大电路的运放具有低电压噪声和高电流噪声的特性。

(以上由地瓜patch/范尼斯特鲁伊于2010-1-11日翻译完成)

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.

将LC电路用作电源滤波器时，若LC滤波器工作在共振频率下将成倍增加电源噪声。将电感换作低Q值电感能够很好得解决这个问题。

13/ Use comparators for comparing and op amps for amplifying and don"t even think of mixing the two.

比较器用作放大，运放用作比较。不要将两者混淆。

14/ Ceramic caps with any other dielectric other than NPO should only be used for bypass applications.

除NPO之外的其他介质的陶瓷电容只能用作旁路电容。

（NPO电容器是电容量和介质损耗最稳定的电容器之一）。

15/ An N-channel enhancement-mode FET needs +ve voltage on the gate-source to conduct form drain-source.

N沟道增强型场效应管需在栅—源端接入正向偏置，来控制漏—源端的导通。

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.

在电流到电压的转换以及低漏电流输入保护的应用中，将小信号结型场效应管的漏端和源端短接用作低漏电流二极管，表现良好。将小信号双极性晶体管的基极和集电极短接也是极好的低漏电流二极管。

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.

Bessel（贝塞尔）型低通滤波器在时域上有最少的过冲量，而Cauer(切比雪夫)型在频域上有最快的衰减速度。

（注一：贝塞尔(Bessel)线性相位滤波器正是由于具有向其截止频率以下的所有频率提供等量延时的特性，才被用于音频设备中，在音频设备中，必须在不损害频带内多信号的相位关系前提下，消除带外噪声。另外，贝塞尔滤波器的阶跃响应很快，并且没有过冲或振铃，这使它在作为音频 DAC 输出端的平滑滤波器，或音频 ADC 输入端的抗混叠滤波器方面，是一种出色的选择。贝塞尔滤波器还可用于分析 D 类放大器的输出，以及消除其它应用中的开关噪声，来提高失真测量和示波器波形测量的精确度。虽然贝塞尔滤波器在它的通频带内提供平坦的幅度和线性相位（即一致的群延时）响应，但它的选择性比同阶（或极数）的巴特沃斯(Butterworth) 滤波器或切比雪夫(Chebyshev)滤波器要差。因此，为了达到特定的阻带衰减水平，需要设计更高阶的贝塞尔滤波器，从而它又需要仔细选择放大器和元件来达到最低的噪声和失真度

注二：切比雪夫滤波器（C auer）是在通带或阻带上频率响应幅度等波纹波动的滤波器。在通带波动的为“I型切比雪夫滤波器”，在阻带波动的为“II型切比雪夫滤波器”。切比雪夫滤波器在过渡带比巴特沃斯滤波器的衰

减快，但频率响应的幅频特性不如后者平坦。切比雪夫滤波器和理想滤波器的频率响应曲线之间的误差最小，但是在通频带内存在幅度波动。

注三：巴特沃斯滤波器的特点是通频带内的频率响应曲线最大限度平坦，没有起伏，而在阻频带则逐渐下降

为零。在振幅的对数对角频率的波得图上,从某一边界角频率开始,振幅随着角频率的增加而逐步减少,趋向负无穷大。）

18/ dB is always 10 times the log of the ratio of 2 powers.

dB = 2*10*lg(A/B)。（这个2是A/B的乘方，放到式子前边）。

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.

低频应用中，晶体管集电极与基极电流的相位相同；在高频，集电极电流相位落后基极90度。在高频振荡器的应用中要重视这一点。

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电路板所最常用的玻璃纤维/环氧树脂（FR4）的介电常数约为4.3。想要做一条阻抗为100ohm的导线，则导线厚度为电路板厚度加上板背面铺地铜箔的厚度的0.4倍。50ohm的导线就是100ohm导线厚度加倍。

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.

将运算跨导放大器能够用作可编程动态电流源时，最主要的是搞清楚什么情况下才能使用这个电流源。

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输出电路配一个射极跟随器可以很好地驱动5v继电器，驱动电压标称为3.5V的继电器表现同样良好，这样即节省了功率又无需反激式元件。