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测试AD603AR的控制与增益之间的关系

news 2026/8/24 15:44:39

压控增益变化运放AD603

测试AD603AR的基本特性
Low Noise 90MHz Variabel Gain Amplifier

01AD603AR的控制特性

一、测试背景

昨天测试了增益可编程运放 AD603AR，由于铺设PCB的引线问题，电路在测量过程中出现了过多的干扰。下面重新对电路PCB铺设进行优化，输入输出信号都使用屏蔽线进行测量。测量一下运放增益变化的特性。

二、测试电路

修改设计的电路。核心放大芯片为ADF603AR。增益控制负向输入被偏置到 2.5V 。正向输入有外部的直流电源提供。通过一个 4 芯端口连接外部的信号源与示波器。铺设单面PCB，制作测试电路板。

三、测试结果

焊接电路，清洗之后进行测试。首先，将 AD603 的输出反馈切断，这样可以提高最高的放大倍数，最大可以达到 40dB。输入峰峰值 0.1V 正弦波，经过放大，输出信号的峰峰值达到了 2V。放大倍数为 20倍，对应 26dB。

增益控制正向电压从 1.5V 变化到 3.5V, 测量输出交流信号有效值。可以看到输出信号的增益变化了大约 12倍左右. 这个变化范围似乎与数据手册对应的不一样. 猜测是因为增益控制负向设置为 2.5V 是否太大了? 也许,降低负向输入偏置电压可以提高增益放大控制范围.

▲ 图1.3.1 增益正向输入电压与输出信号幅度

#!/usr/local/bin/python# -*- coding: gbk -*-#============================================================# TEST1.PY -- by Dr. ZhuoQing 2025-12-11## Note:#============================================================fromheadmimport*fromtsmodule.tsvisaimport*dm3068open()vset=linspace(1.5,3.5,100)vout=[]forvinvset:dh1766volt(v)time.sleep(1.5)ac=dm3068vac()vout.append(ac)printff(v,ac)tspsave("measure",vset=vset,vout=vout)plt.plot(vset,vout,lw=3)plt.xlabel("Vset(V)",color="steelblue",fontsize=24)plt.ylabel("Vout(V)",color="steelblue",fontsize=24)plt.grid(True,which='both',linestyle='--',alpha=0.7)plt.tight_layout()plt.show()#------------------------------------------------------------printf("\a")#------------------------------------------------------------# END OF FILE : TEST1.PY#============================================================

vset=[1.5000,1.5202,1.5404,1.5606,1.5808,1.6010,1.6212,1.6414,1.6616,1.6818,1.7020,1.7222,1.7424,1.7626,1.7828,1.8030,1.8232,1.8434,1.8636,1.8838,1.9040,1.9242,1.9444,1.9646,1.9848,2.0051,2.0253,2.0455,2.0657,2.0859,2.1061,2.1263,2.1465,2.1667,2.1869,2.2071,2.2273,2.2475,2.2677,2.2879,2.3081,2.3283,2.3485,2.3687,2.3889,2.4091,2.4293,2.4495,2.4697,2.4899,2.5101,2.5303,2.5505,2.5707,2.5909,2.6111,2.6313,2.6515,2.6717,2.6919,2.7121,2.7323,2.7525,2.7727,2.7929,2.8131,2.8333,2.8535,2.8737,2.8939,2.9141,2.9343,2.9545,2.9747,2.9949,3.0152,3.0354,3.0556,3.0758,3.0960,3.1162,3.1364,3.1566,3.1768,3.1970,3.2172,3.2374,3.2576,3.2778,3.2980,3.3182,3.3384,3.3586,3.3788,3.3990,3.4192,3.4394,3.4596,3.4798,3.5000]vout=[0.0714,0.0714,0.0714,0.0714,0.0715,0.0715,0.0715,0.0715,0.0716,0.0717,0.0719,0.0722,0.0726,0.0731,0.0739,0.0748,0.0759,0.0774,0.0792,0.0814,0.0840,0.0870,0.0905,0.0943,0.0985,0.1031,0.1079,0.1128,0.1178,0.1229,0.1279,0.1330,0.1383,0.1437,0.1497,0.1566,0.1653,0.1767,0.1936,0.2191,0.2578,0.3177,0.4555,0.6581,0.7869,0.8122,0.8248,0.8315,0.8357,0.8383,0.8399,0.8411,0.8417,0.8422,0.8426,0.8429,0.8430,0.8431,0.8433,0.8435,0.8435,0.8435,0.8434,0.8435,0.8435,0.8435,0.8434,0.8434,0.8435,0.8435,0.8434,0.8433,0.8433,0.8434,0.8433,0.8434,0.8433,0.8433,0.8433,0.8432,0.8433,0.8433,0.8433,0.8434,0.8433,0.8433,0.8434,0.8433,0.8434,0.8433,0.8434,0.8433,0.8434,0.8434,0.8433,0.8433,0.8433,0.8433,0.8432,0.8433]

降低增益控制负输入端电压，将电路中的 R2 修改为 2k欧姆。对应的负向输入电压为 1V。测量输出信号随着增益控制正向输入电压的变化。此时，输入信号为峰峰值 10mV 的 1kHz 的正弦信号。在增益控制电压小于 0.5V 之前，输出交流信号幅度大约为有效值 7mV。当正向电压超过 1.5V之后，输出信号的有效值达到了 0.794V。的确，增益超过了 40dB。在这个过程中，输出信号的幅度出现了一个突变，这有可能是因为此时，电路出现了高频震荡引起的。

▲ 图1.3.2 GNEG设置为 1V 对应的正向控制电压与输出电压

vset=[0.0000,0.0202,0.0404,0.0606,0.0808,0.1010,0.1212,0.1414,0.1616,0.1818,0.2020,0.2222,0.2424,0.2626,0.2828,0.3030,0.3232,0.3434,0.3636,0.3838,0.4040,0.4242,0.4444,0.4646,0.4848,0.5051,0.5253,0.5455,0.5657,0.5859,0.6061,0.6263,0.6465,0.6667,0.6869,0.7071,0.7273,0.7475,0.7677,0.7879,0.8081,0.8283,0.8485,0.8687,0.8889,0.9091,0.9293,0.9495,0.9697,0.9899,1.0101,1.0303,1.0505,1.0707,1.0909,1.1111,1.1313,1.1515,1.1717,1.1919,1.2121,1.2323,1.2525,1.2727,1.2929,1.3131,1.3333,1.3535,1.3737,1.3939,1.4141,1.4343,1.4545,1.4747,1.4949,1.5152,1.5354,1.5556,1.5758,1.5960,1.6162,1.6364,1.6566,1.6768,1.6970,1.7172,1.7374,1.7576,1.7778,1.7980,1.8182,1.8384,1.8586,1.8788,1.8990,1.9192,1.9394,1.9596,1.9798,2.0000]vout=[0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0073,0.0074,0.0077,0.0081,0.0087,0.0095,0.0105,0.0115,0.0125,0.0136,0.0147,0.0160,0.0176,0.0195,0.0217,0.0240,0.0262,0.0284,0.0308,0.0336,0.0372,0.0415,0.0460,0.0505,0.0550,0.0595,0.0648,0.0714,0.0792,0.0881,0.0972,0.1061,0.1149,0.1247,0.1366,0.1511,0.1683,0.1863,0.2043,0.2312,0.2513,0.2745,0.3025,0.3350,0.3698,0.4047,0.4369,0.4682,0.5023,0.5009,0.4983,0.5577,0.6775,0.7184,0.7452,0.7641,0.7761,0.7822,0.7847,0.7866,0.7889,0.7891,0.7913,0.7909,0.7908,0.7906,0.7893,0.7905,0.7921,0.7915,0.7912,0.7929,0.7923,0.7930,0.7935,0.7936,0.7939,0.7945]

将输出反馈回路短接。此时，运放的最大增益为 30dB左右。测量增益控制电压与输出信号幅度的关系。当增益正向输入电压小于 0.5V，输出信号幅度大约为 3.5mV 左右。当增益正向输入电压超过 1.5V，对应输出信号电压为 0.28V。增益电压超过 1.5V之后，运放也处在高频震荡状态。

▲ 图1.3.3 短接输出返回回路之后增益控制与输出信号幅度

vset=[0.0000,0.0202,0.0404,0.0606,0.0808,0.1010,0.1212,0.1414,0.1616,0.1818,0.2020,0.2222,0.2424,0.2626,0.2828,0.3030,0.3232,0.3434,0.3636,0.3838,0.4040,0.4242,0.4444,0.4646,0.4848,0.5051,0.5253,0.5455,0.5657,0.5859,0.6061,0.6263,0.6465,0.6667,0.6869,0.7071,0.7273,0.7475,0.7677,0.7879,0.8081,0.8283,0.8485,0.8687,0.8889,0.9091,0.9293,0.9495,0.9697,0.9899,1.0101,1.0303,1.0505,1.0707,1.0909,1.1111,1.1313,1.1515,1.1717,1.1919,1.2121,1.2323,1.2525,1.2727,1.2929,1.3131,1.3333,1.3535,1.3737,1.3939,1.4141,1.4343,1.4545,1.4747,1.4949,1.5152,1.5354,1.5556,1.5758,1.5960,1.6162,1.6364,1.6566,1.6768,1.6970,1.7172,1.7374,1.7576,1.7778,1.7980,1.8182,1.8384,1.8586,1.8788,1.8990,1.9192,1.9394,1.9596,1.9798,2.0000]vout=[0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0035,0.0036,0.0036,0.0037,0.0039,0.0042,0.0045,0.0050,0.0055,0.0060,0.0065,0.0070,0.0077,0.0084,0.0093,0.0103,0.0114,0.0124,0.0135,0.0146,0.0160,0.0176,0.0196,0.0217,0.0239,0.0261,0.0283,0.0308,0.0340,0.0377,0.0419,0.0464,0.0507,0.0550,0.0597,0.0655,0.0725,0.0806,0.0893,0.0980,0.1065,0.1154,0.1257,0.1382,0.1529,0.1691,0.1856,0.2015,0.2165,0.2287,0.2384,0.2493,0.2617,0.2744,0.2861,0.2969,0.3065,0.3159,0.3264,0.3447,0.3753,0.3884,0.3965,0.4143,0.4204,0.4218,0.4225,0.4232,0.4236,0.4239,0.4240,0.4244,0.4247,0.4247,0.4249,0.4249,0.4249,0.4250,0.4249]