第10章:计算机和电子——营造一个简单的1瓦特功率音频功率放大器

一个简单的1瓦特功率音频功率放大器

The solderless breadboard makes it easy to experiment with additions to the radio circuit. solderless线路板的方便试验用添加收音机电路。In this section, we will build a simple amplifier, so that a whole room can hear the radio through a speaker. 在这一节中,我们将建立一个简单的放大,使整个房间都能听到收音机通过扬声器有关的东西。Our amplifier will not be ear shattering, since we have made it as simple as we can to build, but the output is pretty impressive for a single transistor.我们的放大器会不会耳朵打破,因为我们已经成为了简单的尽我们所能来建,但是输出是相当令人印象深刻的,为一个单一的晶体管。

Click on photo for a larger picture点击图片为一更大的画面

With the amplifier, our radio looks like the photo above.与放大,我们的无线电看起来像照片以上。

 

Below is a closeup of the amplifier section:下面是一个看点放大器的部分:

 

Click on photo for a larger picture点击图片为一更大的画面

 

We carry all the parts for the amplifier (except the battery) in our我们进行所有的放大器配件(除电池)在我们的catalog目录.

The amplifier needs these parts:放大器需要这些部分:

• An MPSW45A Darlington transistor一个MPSW45A晶体管用
  This is the main working part of the amplifier.这是最主要的工作部分放大器的。
• A small speaker一个小的发言人
  
• Two 100,000 ohm resistors两个10欧姆电阻
  This resistor will have four colored bands on it. 这个电阻有四彩色的乐队。The colors will be brown, black, yellow, and gold.颜色将棕、黑、黄、和黄金。
• A 10,000 ohm resistor一家1欧姆电阻
  The colors will be brown, black, orange, and gold.颜色将棕、黑、橙、和黄金。
• A 50 ohm resistor一个50欧姆电阻
  The colors will be green, black, black, and gold.颜色是绿色的,黑色,黑色,和黄金。
• A 9 volt battery clip9伏电池夹
  
• A 9 volt battery9伏电池
  

 

Using the labeled grid as before, the parts are connected this way:使用的标记网格和以前一样,这部分是这连接道:

• Jumper wire: J22 to I27跳线对I27 J22:
• 10,000 ohm resistor( brown, black, orange): G20 to F2810000欧姆电阻(棕色、黑、橙):二十国集团,F28
• 100,000 ohm resistor( brown, black, yellow): H27 to H2810欧姆电阻(棕色,黑色,黄色):H27到H28
• 100,000 ohm resistor( brown, black, yellow): I28 to I2910欧姆电阻(棕色,黑色,黄色):I28到I29
• MPSW45A: J27, J28, and J29MPSW45A:J27,J28,J29
• 50 ohm resistor( green, black, black): I33 to I3450欧姆电阻(绿、黑色、黑色):I33到I34
• Speaker: F29 to J33广播员:F29 J33,
• Negative 9 volt battery wire (black): F26负9伏电池线(黑色):F26
• Positive 9 volt battery wire (red): F34积极的9伏电池线(红):F34

 

 

 

 

A more permanent version一种更持久的版本

As before, we can copy the circuit onto a printed circuit board and solder all of the parts firmly in place.一如既往,我们可以拷贝电路在印制线路板及焊接所有的零件紧紧地按在伤口处。

Click on photo for a larger picture点击图片为一更大的画面

 

Click on photo for a larger picture点击图片为一更大的画面

 

Click on photo for a larger picture点击图片为一更大的画面

 

 

 

How does it do that?它如何做呢?

The heart of the amplifier is the transistor. 放大器的心是晶体管。We could have used a more ordinary NPN transistor, such as the 2N4401, but to get a louder sound, we use a special "two-in-one" type of transistor called a Darlington.我们本可以使用普通的NPN晶体管,如2N4401,而是为了去一个较响亮的声音,我们用一种特殊的“无类晶体管称为可能出战。

 

Click on photo for a larger picture点击图片为一更大的画面

 

The Darlington transistor has two transistors in the same package, and can amplify signals much more than a single transistor can.用的晶体管有两个晶体管在相同的包中,并能放大信号远远超过一个晶体管单管。

Transistors amplify a signal by acting like a variable resistor. 晶体管放大信号表现得像一个可调电阻器。We put the signal in at the base, and the signal controls how much current goes through the transistor from the emitter to the collector.我们把信号在在该基地,和信号控制多少电流经过晶体管区的收集器。

If we simply put the signal into the base, however, the transistor would turn off completely when the signal was low, and turn on completely when the signal is high. 如果我们只是把这信号转化为基础,然而,晶体管会关掉完全信号是低的,和打开完全信号高。This behavior is useful when we want to use the transistor as a switch, but we have to change the behavior to make a good audio amplifier.这种行为有用,当我们想要使用晶体管作为一个开关,可我们不得不改变行为给她留下一个好音频功率放大器。

When the signal is at zero, we want the output of the amplifier to be halfway between 0 and 9 volts (4.5 volts). 当电信号为零,我们要输出放大器的是介于0到9伏的一半(4.5伏特)。We can arrange for this to happen by using a voltage divider. 我们可以安排这种情况发生,利用一个电压分压器。A voltage divider is two resistors, one connected to the positive side of the battery, and the other to the negative side. 一个电压分压器两电阻,一个连接到积极的一面的电池,并另一条通向消极的一面。Where they meet in the middle, the voltage will be divided in half (if the resistors are the same).在那里他们在中间碰面,电压将分成两半(如果电阻器是相同的)。

Since current flows through the resistors all the time, we want their values to be high, so that not much current flows through them. 因为的电流通过电阻器的,所以我们希望他们的价值高,所以电流通过这一点。This will prevent them from getting hot, and make the battery last longer. 这就可以防止他们染上热,让电池寿命长。In our circuit we use 100,000 ohms.在我们的电路我们用十万欧姆。

Large resistors in the voltage divider also make it easier for the signal to push the voltage higher or lower. 大电阻的电压分压器也方便信号推动电压更高或更低。This is a good thing, since it means our amplifier will be more sensitive. 这是一件好事,因为它意味着我们的放大器会更敏感。In our case, the signal from the radio is a little too strong, and the signal pushes the voltage too high and too low, causing distortion. 在我们的例子里,这个信号从收音机有点太大,和信号推动电压过高,过低,造成失真。So, we add another resistor, with 10,000 ohms, to match the signal to our amplifier.所以,我们增加一个电阻、用一欧姆时是87,匹配的信号送给我们的放大器。

The transistor can handle 1 watt before it gets too hot, reducing its lifetime. 晶体管能处理1瓦特功率在天气变得太热之前,降低了一生。If we let the full 9 volts get in, the circuit would draw over 2 watts, and while the sound would be nice and loud, the transistor would get quite hot, and the battery would not last long. 如果我们让全9伏电路进去的时候,会把2美国瓦茨时,那么声音就是好又大声、晶体管会变得相当地热,电池能够活不了多久。To make the amplifier draw only one watt, we put in a 50 ohm resistor to lower the current. 使放大器画只有一个瓦特,我们付出了50欧姆电阻降低电流。You may have noticed in the photos that I actually used 100 ohms for the prototype, to keep the noise level down in the lab. 我们已经注意到我的照片里100欧姆实际使用的样机的噪音水平,保持了实验室。You can think of this resistor as a volume control, although you can't adjust it without picking another resistor. 你能想到的这个电阻作为体积控制,尽管你不能把它没有选择另一个电阻。A variable resistor that can handle 2 watts and went from 50 ohms to 150 ohms would let you vary the volume. 一个可调电阻器,能容纳2瓦特,就从50欧姆150欧姆会让你改变该卷。We will leave that modification to the experimenter.我们将把改进的生命。