科技英语考试句子

They can be used to amplify the small output current from a logic chip so that it can operate

他们放大逻辑芯片输出的小电流，从而来驱动灯、继电器或其他大电流器件

A transistor may be used as a switch~and asan

三极管也可用于开关（或是完全导通，流过最大电源，或是完全关断，没有电流流过）和放大器（总是不完全导通）

Transistors can be damaged by heat when soldering so if you are not an expert it is wise

三极管会被焊接时产生的热量所损坏，因此如果你不是这方面的专家，那么最好在焊接点与三极管管身之间的管脚上夹一个散热

Whether the device in question be voltage controlled or current controlled,the amount of

不管讨论的器件是受电压控制还是受电流控制，控制信号所需的功率一般远小于被控信号所用的功率

It is a fundamental rule of physics that energy

能量既不会被创造也不会被消灭，这正是物理学的一个基本法则

If this Law is true and an overwhelming mass of experimental data suggests that it is-then iti

如果这条定律是正确的—惊人的实验数据说明它是正确的—那么就不可能制造出一种器件，该器件可以吸收小能量，然后神奇的把小能量转换为大能量

Usually,machines fail even to meet this limit,losing some of their input energy in the f

通常，机器不能达到这个上限，会以热的形式丢失掉部分输入能量，该部分能量辐射到周围的空间，因此这部分能量不属于输出能量部分

Not only would such a perpetual motion machine prove that the Law of Energy~

这样的永动机不仅能够证明能量守恒定律不成立，而且它能够引导一场前所未有的技术革命，因为它可以循环的给自身提供能量并产生免费的多余能量

The key to understanding how amplifiers can exist without violating the Law of Energy co~

明白放大器能够存在而不违反能量守恒定律的关键在于有源元件的性质

The Law of Energy conservation is not violated because the additional power is suppli 能量守恒定律并没有被违背，因为增加的功率是由外部电源提供的，通常是直流电池或等效电源

Because the efficiency of an amplifier is always 100 percent or less,one can never be m

由于放大器的效率一定为100%或小于100%，任何东西都不可能被做成具有永动功能的装置

One key to the usefulness of these little circuits is in the engineering principle of feedback,particularly negative feedback,which

这些小电路发挥作用的关键在于工程学中的反馈原理，特别是负反馈，其构成了几乎所有自动控制过程的基础

The peak-to-peak amplitude of this amplifier's

Output between cutoff and saturation remains

放大器处于截至饱和状态间的峰峰值保持不变

Large forward transfer function

正向传递函数很大

Virtually nonexistent reverse transfer function

事实上不存在反向传递函数

Large input impedance,Zin

输入阻抗很大，Z（任何信号都可加到运算放大器上而不存在带负载问题）

Small output impedance,Zout

输入阻抗很小，Z（运放提供的功率没有限制）

Wide bandwidth

带宽宽

Infinite gain

增益无穷大

This polarity inversion from input to output is due to the fact that the input signal is being se

输入与输出间极性相反是由于输入信号被夹在运放的反向输入端，因此其相当于反相放大器However,if we apply a constant,positive voltage to the input,the op-amp output will fall

Negative at a linear rate,in an attempt to produce the changing voltage across the capacitor necessary to maintain the current est

可是，如果我们将产生一个恒定的正电压加到输入端，运放的输出将为一个线性的负电压，为了在电容上产生一个变化的电压，有必要维持电阻端电压产生的电流不变

Transmitter:the transmitter converts the message into a signal,the form of which is suitable for transmission over the communicat

发信机。发信机把消息转变为信号，信号形式要适合在通信信道中传送

Receiver:the receiver can be thought of as the inverse of the transmitter ,it changes the received signal back into a message and passes the message onto its destination which

接收机：接收机可以看作是与发信机相反的东西。他把接收到的信号变回成信息，并把消息传给终端，这个终端可以是一台扬声器、电传打字机或一个计算机数据库

This unwanted noise may cause distortions of sound in a telephone,or errors in a telegraph

这种人们不希望存在的噪声会引起电话声音失真，电报报文或数据出现差错

Groups or supergroups are moved as single units by the communications equipment and it is not necessary for the radios to know how many channels are involved

通信设备把群或者超群做为一些单一的单元来传送。对于无限设备来说，并不需要知道含有多少路。

A radio can handle a supergroup provided sufficient bandwidth is available

只要有足够的带宽，无线电可以处理一个超群

The size of the group is a compromise as treating each channels individually involves far more equipment because separate filters,modulators and oscillators are required 群的大小采取折中考虑确定，因为处理每一路都需要独立的滤波器、调制器、振荡器，这比每个群所需的设备要多得多

However the failure of one module will lose all of the channels associated with a group