人们经常对运放采用串联终结方式,以匹配负载的阻抗。但这种实用方法会在终结电阻上产生3dB的输出功率损耗(图1)。较新型运放采用3V和5V工作,限制了输出摆幅,这意味着应避免采用串联匹配电阻方法。另一种办法是用一个串联反馈电路来设定输出阻抗。在40多年前,GTE Lenkurt电子公司的一名高级研究工程师John Wittman就介绍过这一技术。 People often use serial termination of op amps to match the impedance of the load. But this kind of practical method will produce 3dB output power loss on the termination resistance (Fig. 1). The newer op amps, which operate at 3V and 5V, limit the output swing, which means avoiding the use of a series matching resistor approach. Another approach is to use a series feedback circuit to set the output impedance. More than 40 years ago, John Wittman, a senior research engineer at GTE Lenkurt Electronics, introduced the technology.