三极管的工作原理

三极管的工作原理 对三极管放大作用的理解，切记一点:能量不会无缘无故的产生，所以，三极管一定不会产生能量。 但三极管厉害的地方在于:它可以通过小电流去控制大电流。 放大的原理就在于:通过小的交流输入，控制大的静态直流。 假设三极管是个大坝，这个大坝奇怪的地方是，有两个阀门，一个大阀门，一个小阀门。小阀门可以用人力打开，大阀门很重，人力是打不开的，只能通过小阀门的水力打开。 所以，平常的工作流程便是，每当放水的时候，人们就打开小阀门，很小的水流涓涓流出，这涓涓细流冲击大阀门的开关，大阀门随之打开，汹涌的江水滔滔流下。 如果不停地改变小阀门开启的大小，那么大阀门也相应地不停改变，假若能严格地按比例改变，那么，完美的控制就完成了。 在这里，Ube就是小水流，Uce就是大水流，人就是输入信号。当然，如果把水流比为电流的话，会更确切，因为三极管毕竟是一个电流控制元件。 如果某一天，天气很旱，江水没有了，也就是大的水流那边是空的。管理员这时候打开了小阀门，尽管小阀门还是一如既往地冲击大阀门，并使之开启，但因为没有水流的存在，所以，并没有水流出来。这就是三极管中的截止区。 饱和区是一样的，因为此时江水达到了很大很大的程度，管理员开的阀门大小已经没用了。如果不开阀门江水就自己冲开了，这就是二极管的击穿。 在模拟电路中，一般阀门是半开的，通过控制其开启大小来决定输出水流的大小。没有信号的时候，水流也会流，所以，不工作的时候，也会有功耗。 而在数字电路中，阀门则处于开或是关两个状态。当不工作的时候，阀门是完全关闭的，没有功耗。 结构与操作原理 三极管的基本结构是两个反向连结的pn接面，如图1所示，可有pnp和npn 两种组合。三个接出来的端点依序称为射极(emitter, E)、基极(base, B)和集 极(collector, C)，名称来源和它们在三极管操作时的功能有关。图中也显示出 npn与pnp三极管的电路符号，射极特别被标出，箭号所指的极为n型半导体， 和二极体的符号一致。在没接外加偏压时，两个pn接面都会形成耗尽区，将中 性的p型区和n型区隔开。 图1 pnp(a)与npn(b)三极管的结构示意图与电路符号。 三极管的电特性和两个pn接面的偏压有关，工作区间也依偏压方式来分类，这里 我们先讨论最常用的所谓”正向活性区”(forward active)，在此区EB极间的pn接 面维持在正向偏压，而BC极间的pn接面则在反向偏压，通常用作放大器的三极管 都以此方式偏压。图2(a)为一pnp三极管在此偏压区的示意图。 EB接面的空乏 区由于在正向偏压会变窄，载体看到的位障变小，射极的电洞会注入到基极，基 极的电子也会注入到射极;而BC接面的耗尽区则会变宽，载体看到的位障变大， 故本身是不导通的。图2(b)画的是没外加偏压，和偏压在正向活性区两种情形 下，电洞和电子的电位能的分布图。 三极管和两个反向相接的pn二极管有什么差别呢,其间最大的不同部分就在 于三极管的两个接面相当接近。以上述之偏压在正向活性区之pnp三极管为例， 射极的电洞注入基极的n型中性区，马上被多数载体电子包围遮蔽，然后朝集电极 方向扩散，同时也被电子复合。当没有被复合的电洞到达BC接面的耗尽区时， 会被此区内的电场加速扫入集电极，电洞在集电极中为多数载体，很快藉由漂移电流 到达连结外部的欧姆接点，形成集电极电流IC。 IC的大小和BC间反向偏压的大小 air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting,air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting, 关系不大。基极外部仅需提供与注入电洞复合部分的电子流IBrec，与由基极注入 射极的电子流InB? E(这部分是三极管作用不需要的部分)。 InB? E在射极与与电 洞复合，即InB? E=I。pnp三极管在正向活性区时主要的电流种类可以清楚地 Erec 在图3(a)中看出。 图2 (a)一pnp三极管偏压在正向活性区;(b)没外加偏压，和偏压在正向 活性区两种情形下，电洞和电子的电位能的分布图比较。 图3 (a) pnp三极管在正向活性区时主要的电流种类;(b)电洞电位能分布及 注入的情形;(c)电子的电位能分布及注入的情形。 一般三极管设计时，射极的掺杂浓度较基极的高许多，如此由射极注入基极 的射极主要载体电洞(也就是基极的少数载体)IpE? B电流会比由基极注入射极 的载体电子电流InB? E大很多，三极管的效益比较高。图3(b)和(c)个别画出电洞 和电子的电位能分布及载体注入的情形。同时如果基极中性区的宽度WB愈窄， 电洞通过基极的时间愈短，被多数载体电子复合的机率愈低，到达集电极的有效电 洞流IpE? C愈大，基极必须提供的复合电子流也降低，三极管的效益也就愈高。 集电极的掺杂通常最低，如此可增大CB极的崩溃电压，并减小BC间反向偏压的 pn接面的反向饱和电流，这里我们忽略这个反向饱和电流。 由图4(a)，我们可以把各种电流的关系写下来: 射极电流 基极电流 集电极电流 三极管的工作原理(2) 2010年03月08日 星期一 11:07 三极管截止与饱合状态 截止状态 三极管作为开关使用时，仍是处于下列两种状态下工作。 1.截止(cut off)状态:如图5所示，当三极管之基极不加偏压或 加上反向偏压使BE极截止时(BE极之特性和二极管相同，须加 上大于0.7V之正向偏压时才态导通)，基极电流IB=0，因为IC=β IB，所以IC=IE=0，此时CE极之间相当于断路，负载无电流。 (c)此时集极(C)与射极(E) a)基极(B)不加偏压使 (b)基极(B)加上反向偏 之间形同段路，负载无 基极电流IB等于零 压使基极电流IB等于零 电流通过 图5 三极管截止状态 饱合状态 饱合(saturation)状态:如图6所示，当三极管之基极加入驶 air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting,air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting, 大的电流时，因为IC?IE=β×IB，射极和集极的电流亦非常大，此 时，集极与射极之间的电压降非常低(VCE为0.4V以下)，其意义相 当于集极与射极之间完全导通，此一状态称为三极管饱合。 图6 (a)基极加上足够的顺向 (b)此时C-E极之间视同 偏压使IB足够大 导通 状态 晶体管的电路符号和各三个电极的名称如下 图7 PNP型三极管 图8 NPN型三极管 三极管的特性曲线 1、输入特性 图2 (b)是三极管的输入特性曲线，它表示Ib随Ube的变化关系，其特点是:1)当Uce在0-2伏范围 内，曲线位置和形状与Uce有关，但当Uce高于2伏后，曲线Uce基本无关通常输入特性由两条曲线 (?和?)表示即可。 2)当Ube,UbeR时，Ib?O称(0,UbeR)的区段为“死区”当Ube,UbeR时，Ib随Ube增加而增加， 放大时，三极管工作在较直线的区段。 3)三极管输入电阻，定义为: rbe=(?Ube/?Ib)Q点，其估算公式为: rbe=rb+(β+1)(26毫伏/Ie毫伏) rb为三极管的基区电阻，对低频小功率管，rb约为300欧。 2、输出特性 输出特性表示Ic随Uce的变化关系(以Ib为参数)从图9(C)所示的输出特性可见，它分为三个区域: 截止区、放大区和饱和区。 截止区当Ube,0时，则Ib?0，发射区没有电子注入基区，但由于分子的热运动，集电集仍有小量电流 通过，即Ic=Iceo称为穿透电流，常温时Iceo约为几微安，锗管约为几十微安至几百微安，它与集电极 反向电流Icbo的关系是: Icbo=(1+β)Icbo air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting,air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting, 常温时硅管的Icbo小于1微安，锗管的Icbo约为10微安，对于锗管，温度每升高12?，Icbo数值增加一倍，而对于硅管温度每升高8?， Icbo数值增大一倍，虽然硅管的Icbo随温度变化更剧烈，但由于锗管的Icbo值本身比硅管大，所以锗管仍然受温度影响较严重的管，放大区，当晶体三极管发射结处于正偏而集电结于反偏工作时，Ic随Ib近似作线性变化，放大区是三极管工作在放大状态的区域。 饱和区当发射结和集电结均处于正偏状态时，Ic基本上不随Ib而变化，失去了放大功能。根据三极管发射结和集电结偏置情况，可能判别其工作状态。 图9 三极管的主要参数 1、直流参数 (1)集电极一基极反向饱和电流Icbo，发射极开路(Ie=0)时，基极和集电极之间加上规定的反向电压Vcb时的集电极反向电流，它只与温度有关，在一定温度下是个常数，所以称为集电极一基极的反向饱和电流。良好的三极管，Icbo很小，小功率锗管的Icbo约为1,10微安，大功率锗管的Icbo可达数毫安培，而硅管的Icbo则非常小，是毫微安级。 (2)集电极一发射极反向电流Iceo(穿透电流)基极开路(Ib=0)时，集电极和发射极之间加上规定反向电压Vce时的集电极电流。 Iceo大约是Icbo的β倍即Iceo=(1+β)Icbo o Icbo和Iceo受温度影响极大，它们是衡量管子热稳定性的重要参数，其值越小，性能越稳定，小功率锗管的Iceo比硅管大。 (3)发射极---基极反向电流Iebo集电极开路时，在发射极与基极之间加上规定的反向电压时发射极的电流，它实际上是发射结的反向饱和电流。 (4)直流电流放大系数β1(或hEF)这是指共发射接法，没有交流信号输入时，集电极输出的直流电流与基极输入的直流电流的比值，即: β1=Ic/Ib 2、交流参数 (1)交流电流放大系数β(或hfe)这是指共发射极接法，集电极输出电流的变化量?Ic与基极输入电流的变化量?Ib之比，即: β= ?Ic/?Ib 一般电晶体的β大约在10-200之间，如果β太小，电流放大作用差，如果β太大，电流放大作用虽然大，但性能往往不稳定。 (2)共基极交流放大系数α(或hfb)这是指共基接法时，集电极输出电流的变化是?Ic与发射极电流的变化量?Ie之比，即: α=?Ic/?Ie 因为?Ic,?Ie，故α,1。高频三极管的α,0.90就可以使用 α与β之间的关系: α= β/(1+β) β= α/(1-α)?1/(1-α) (3)截止频率fβ、fα当β下降到低频时0.707倍的频率，就什发射极的截止频率fβ;当α下降到低频时的0.707倍的频率，就什基极的截止频率fαo fβ、 fα是表明管子频率特性的重要参数，它们之间的关系 air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting,air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting, 为: fβ?(1-α)fα (4)特征频率fT因为频率f上升时，β就下降，当β下降到1时，对应的fT是全面地反映电晶体的高 频放大性能的重要参数。 3、极限参数 (1)集电极最大允许电流ICM当集电极电流Ic增加到某一数值，引起β值下降到额定值的2/3或1/2， 这时的Ic值称为ICM。所以当Ic超过ICM时，虽然不致使管子损坏，但β值显著下降，影响放大品质。 (2)集电极----基极击穿电压BVCBO当发射极开路时，集电结的反向击穿电压称为BVEBO。 (3)发射极-----基极反向击穿电压BVEBO当集电极开路时，发射结的反向击穿电压称为BVEBO。 (4)集电极-----发射极击穿电压BVCEO当基极开路时，加在集电极和发射极之间的最大允许电压，使 用时如果Vce,BVceo，管子就会被击穿。 (5)集电极最大允许耗散功率PCM集电流过Ic，温度要升高，管子因受热而引起参数的变化不超过允 许值时的最大集电极耗散功率称为PCM。管子实际的耗散功率于集电极直流电压和电流的乘积，即 Pc=Uce×Ic.使用时庆使Pc,PCM。 PCM与散热条件有关，增加散热片可提高PCM。 三极管的工作原理(3) 2010年03月08日 星期一 11:08 晶体三极管用途 晶体三极管的用途主要是交流信号放大，直流信号放大和电路开关。 晶体三极管偏置 使用晶体管作放大用途时，必须在它的各电极上加上适当极性的电压，称为“偏置电压”简称“偏压”， 又“偏 置偏流”。电路组成上叫偏置电路。 晶体管各电极加上适当的偏置电压之后，各电极上便有电流流动。 通过发射极的电流称为“射极电流”，用 IE表示;通过基极的电流称为“基极电流”，用IB表示;通过集电极的电流称为“集极电流”，用IC表示。 图10 晶体管三个电极的电流有一定关系，公式如下 IE , IB ，IC air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting,air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting, 晶体三极管的三种放大电路 三极管放大电路 当晶体管被用作放大器使用时，其中两个电极用作信号 (待放大信号) 的输入端子;两个电极作为 信号 (放大后的信号) 的输出端子。 那么，晶体管三个电极中，必须有一个电极既是信号的输入端子， 又同时是信号的输出端子，这个电极称为输入信号和输出信号的公共电极。 按晶体管公共电极的不同选择，晶体管放大电路有三种:共基极电路 (Common base circuit)、共 射极电路(Common emitter circuit) 和 共集极电路(Common collector circuit)，如下图示。 图11 由于共射极电路放大电路的电流增益和电压增益均较其它两种放大电路为大，故多用作讯号放大使用。 晶体三极管的放大作用晶体管是一个电流控制组件，其集极电流 IC可以由基极电流IB控制，只需轻微的改变基流IB就可以引起很大的集流变化IC。由于晶体管基流IB的轻微变化可以控制较大的集流IC，我们利用这一特点，用它来放大微弱的电信号，称为晶体管的放大作用 (Amplification)，简称晶体管放大。简单来说，晶体管的放大原理是把微弱的电信号 (微弱的电压信号 Vi) 加在基极上，使基极电流按电信号变化，通过晶体管的电流控制作用，就可以在负载上得到与原信号变化一样，但增强了的电信号 (较大的电压信号 Vo)。 air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting,air, keep house air fresh, cooling, moisture, reduce the body temperature of the chicken, which is a measure of the chicken house the first element of the environment. (1) the parameters: ventilation in summer peak demand calculations, 4~5 cubic metres per kilogram of body weight per hour, harmful gas concentration does not exceed 20ppm ammonia, hydrogen sulfide, l0ppm, co 0.15%. (2) ventilation natural ventilation and mechanical ... 5. thermal insulation roof cold season is the region of greatest heat loss, are also hot towel sunlight than any other region, so the roof insulation is the most important region, followed by the walls, if open sheds to make doors and Windows switches freely, and seal well. On most of the walls and roof insulation must be taken or equivalent devices, thermal insulation materials require higher thermal resistance, good thermal insulation properties, and thicken the North wall must also be taken of thickness and measures such as roof and ceiling canopy. In places with more rain, due the eaves of roofs on both sides extending outward. Pheasants (pheasants) farm building (a) site choose pheasant fields should be selected gaozao terrain, sand texture, well drained, slightly to the South of terrain. Mountain areas should be selected under the sunny, spacious, ventilation, sunshine, where the drainage is good. Pheasant farms should be built in a quiet, safe place, away from residential areas, factories, the main traffic artery, but taking into account feed, transportation problems. A clean water source, water is not contaminated. To have a reliable power supply, not only to maintain normal lighting,