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问 大家好，
我使用的DAC是电流输出，峰峰值10毫安，因为是电流输出，所以输出电阻很大很大，估计有几百K到几兆欧姆，现在输出要和一个50欧姆的电阻匹配。

产家的DataSheet上面说用射频变压器，如图所示，这个电路俺不会分析了，确切的说，按照我的分析，它的阻抗是不匹配的。。。。它工作在大几十兆的的频率，如果阻抗不匹配，VSWR会很大，影响电路的性能。所以俺想搞明白这个东西，因为，我不是和50欧姆匹配，俺适合200欧姆的下一级电路匹配。希望高手指明原理，然后我可以去设计俺的200欧姆匹配电路。

谢谢！


电路说明的具体描述摘抄如下：
An RF transformer CAN be used to perform a differential-to-single-ended signal conversion, as shown in Figure 20.A
differentially-coupled transformer output provides the optimum distortion performance for output signals whose spectral content lies within the transformer’s pass band. An RF transformer such as the Mini-Circuits T1–1T provides excellent rejection of common-mode distortion (i.e., even-order hARMonics) and noise over a wide frequency range. When IOUTA and IOUTB are terminated to ground with 50 ohm, this configuration provides 0 dBm power to a 50 ohm load on the secondary with a DAC fullscale current of 20 mA. A 2:1 transformer such as the Coilcraft WB2040-PC CAN also be used in a configuration in which IOUTA and IOUTB are terminated to ground with 75 ohm. This configuration improves load matching and increases power to 2 dBm into a 50ohm load on the secondary. Transformers with different impedance ratios may also be used for impedance matching purposes. Note that the transformer provides ac coupling only. The center tap on the primary side of the transformer must be
connected to ACOM to provide the necessary dc current path for both IOUTA and IOUTB. The complementary voltages appearing
at IOUTA and IOUTB (i.e., VOUTA and VOUTB) swing symmetrically around ACOM and should be maintained with the specified
output compliance range of the AD9755. A differential resistor, RDIFF, may be inserted into applications where the output of the transformer is connected to the load, RLOAD, via a passive reconstruction filter or cable. RDIFF is determined by the transformer’s impedance ratio and provides the proper source termination that results in a low VSWR. 答 1: 对了，还有下一级负载的电压怎么计算哦。。。对了，还有一个很重要，就是，所设计的匹配电路，它的负载有多少的电压，我的下一级电路不能过载！