LM311输出限流模式LM311,LM211,LM111**AD\Test\2026\September\TestLM211OutputCurrentLimit.SchDoc ***01【LM311 比较器输出限流】一、测量电路这是比较器LM311它内部的参考电路图 在它的输出端被称之为隔离的三极管 它可以接地或者是负电源 我们能看到它的输出端有一个限流电阻四欧姆。 从逻辑图上可以看到 当流过电流大的时候 它会使得左边三极管导通。 进而拉低它上面的三极管的基极的电压 天使的输出电压下降。 由此可以对输出电流进行限流。 那么究竟在实际过程中 这个电流上限是多少 我们下面通过测试电路板进行测试在测试电路图中 我们配置比较器的正负输入电压 使得输出为低电平 也就是输出三极管导通 使用上面10欧姆的电阻来测量流过三极管电流的大小。 同时测量输出电压的大小 这样我们可以获得输出三极管的电压与电流。 铺设单面PCB适合一分钟制板 一分钟之后我们得到测试电路板电路板制作的非常完美下面焊接测试。二、测试结果焊接电路板使用高温水蒸气进行清洗 首先给电路提供正5伏的工作电源 LM311的输入端 使用dh1766施加从03伏的电压 在每个电压上测量 LM311它的输出端口的电压 以及通过采样电阻测量电流的大小 这样便可以获得LM311在输出低电平下 它输出端口的电流电压特性 由此我们可以明显看到 它当输入端口的电压超过1.5伏之后 它对应的灌入电流去向恒流模式 这也验证了前面我们从它内部等效原理图分析得到的对应的输出限流的恒流模式。vce[-0.0009,0.0260,0.0529,0.0769,0.0997,0.1201,0.1397,0.1578,0.1758,0.1848,0.2095,0.2262,0.2420,0.2581,0.2735,0.2893,0.3044,0.3199,0.3349,0.3503,0.3655,0.3803,0.3953,0.4100,0.4248,0.4394,0.4543,0.4688,0.4842,0.4979,0.5136,0.5285,0.5430,0.5578,0.5723,0.5851,0.6015,0.6164,0.6307,0.6455,0.6599,0.6720,0.6896,0.7039,0.7188,0.7331,0.7479,0.7622,0.7770,0.7914,0.8062,0.8206,0.8354,0.8502,0.8647,0.8796,0.8940,0.9016,0.9233,0.9381,0.9524,0.9671,0.9815,0.9963,1.0124,1.0257,1.0405,1.0550,1.0699,1.0843,1.0991,1.1134,1.1283,1.1430,1.1581,1.1736,1.1886,1.2041,1.2190,1.2343,1.2493,1.2649,1.2801,1.2960,1.3047,1.3281,1.3450,1.3618,1.3697,1.3969,1.4162,1.4363,1.4585,1.4820,1.5084,1.5367,1.5658,1.5972,1.6288,1.6619]ice[-0.0024,0.0167,0.0510,0.1022,0.1740,0.2586,0.3580,0.4630,0.5778,0.6977,0.8176,0.9447,1.0700,1.2010,1.3299,1.4644,1.5958,1.7325,1.8662,2.0049,2.1441,2.2791,2.4188,2.5550,2.6964,2.8339,2.9761,3.1142,3.2570,3.3956,3.5387,3.6823,3.8216,3.9654,4.1049,4.2489,4.3880,4.5321,4.6710,4.8152,4.9551,5.0995,5.2436,5.3827,5.5264,5.6654,5.8088,5.9477,6.0915,6.2308,6.3741,6.5124,6.6556,6.7986,6.9379,7.0805,7.2187,7.3611,7.4984,7.6397,7.7756,7.9152,8.0517,8.1919,8.3309,8.4658,8.6063,8.7422,8.8821,9.0154,9.1537,9.2862,9.4245,9.5594,9.6994,9.8402,9.9769,10.1168,10.2493,10.3859,10.5179,10.6540,10.7837,10.9177,11.0494,11.1747,11.3016,11.4195,11.5329,11.6347,11.7333,11.8176,11.8914,11.9474,11.9874,12.0090,12.0141,12.0080,11.9937,11.9746]fromheadmimport*fromtsmodule.tsvisaimport*fromtsmodule.tsstm32import*vdimlinspace(0,3,100)vce[]ice[]R10dm3068open()forvinvdim:dh1766volt1(v)time.sleep(1)vidm3068vdc()ivi/R*100ice.append(i)metermeterval()vvmeter[0]vce.append(vv)printff(v,vv,i)tspsave(measure,vcevce,iceice)dh1766volt1(0)plt.plot(vce,ice,lw3)plt.xlabel(Vce(V),colorsteelblue,fontsize24)plt.ylabel(Ice(mA),colorsteelblue,fontsize24)plt.grid(True,whichboth,linestyle--,alpha0.7)plt.tight_layout()plt.show()重新再测量一次这次将输入端口的电压从0伏扩展到5伏 可以看到在1.5伏之前 所测的特性和之前是一样的 明显看到当端口电压超过1.5伏之后 对应的电流呈现下降趋势。 而且下降的过程中它的波动并不是一种有规律的情况 但是猜测它之所以下降 一种可能性是内部恒温机制有过热保护 也有可能是在电压超过1.5伏之后 芯片内部发热这种温度系数使得它限流。 输出的容量继续减小 但不论哪一种方式造成它下降过程中这种不规律的情况具体原因尚未可知。vce[-0.0004,0.0441,0.0839,0.1195,0.1515,0.1813,0.2097,0.2371,0.2638,0.2900,0.3159,0.3415,0.3668,0.3913,0.4163,0.4411,0.4659,0.4905,0.5150,0.5395,0.5640,0.5885,0.6128,0.6372,0.6611,0.6854,0.7098,0.7339,0.7582,0.7825,0.8067,0.8309,0.8564,0.8785,0.9052,0.9293,0.9539,0.9785,0.9989,1.0287,1.0533,1.0782,1.1030,1.1279,1.1530,1.1779,1.2024,1.2275,1.2530,1.2790,1.3051,1.3317,1.3589,1.3882,1.4200,1.4560,1.4954,1.5406,1.5898,1.6424,1.6936,1.7561,1.8262,1.9085,2.0102,2.1158,2.1946,2.2514,2.3165,2.3724,2.4292,2.4893,2.5491,2.6071,2.6673,2.7190,2.7805,2.8450,2.8987,2.9559,3.0102,3.0605,3.1142,3.1699,3.2246,3.2786,3.3359,3.3994,3.4682,3.5053,3.6466,3.7283,3.8163,3.8871,3.9427,3.9989,4.0557,4.1128,4.1701,4.2274]ice[-0.0027,0.0426,0.1313,0.2674,0.4359,0.6245,0.8258,1.0359,1.2517,1.4727,1.6969,1.9236,2.1524,2.3776,2.6094,2.8423,3.0760,3.3103,3.5449,3.7804,4.0168,4.2529,4.4893,4.7262,4.9585,5.1949,5.4309,5.6679,5.9046,6.1414,6.3770,6.6130,6.8489,7.0831,7.3179,7.5486,7.7834,8.0175,8.2516,8.4872,8.7223,8.9564,9.1890,9.4205,9.6516,9.8803,10.1032,10.3306,10.5577,10.7823,11.0002,11.2119,11.4159,11.6088,11.7776,11.9144,12.0069,12.0531,12.0574,12.0370,12.0050,11.9226,11.7506,11.4655,11.0049,10.5120,10.2595,10.1394,10.0714,10.0135,9.9577,9.8737,9.7908,9.7216,9.6338,9.6203,9.5135,9.3906,9.3596,9.3003,9.2578,9.2639,9.2319,9.1864,9.1508,9.1161,9.0500,8.9358,8.7718,8.5617,7.9124,7.7536,7.5959,7.2443,7.1905,7.1357,7.0771,7.0174,6.9556,6.8927]※总结 ※本文根据高速比较器LM311内部等效电路 可以看到它的输出具有限流的模式。 通过实际测试可以看到它的输出最大电流大约是在12毫安左右 这种线的模式可以进一步保护输出驱动管不要进入过度饱和状态 在另一方面也限制了输出短路对芯片造成的损伤。■ 相关文献链接:LM311,LM211,LM111