Negative-feedback amplifier with accurately defined input or output impedance combined with high or low output or input impedance respectively

摘要

Negative-feedback amplifier provided with an active amplifier section operating approximately as a nullor and a negative feedback section, the amplifier having a high loop gain. The active amplifier section is constructed in balanced form with two nullors connected in balance, and the negative-feedback section is composed of passive impedances and comprises two negative-feedback loops. In one embodiment each nullor has a series-coupling circuit and a parallel-coupling circuit at the input port. As a result an accurately defined or characteristic input impedance is obtained, and a series- or parallel-coupling circuit is formed in both negative-feedback loops at the output port, so that a high (current output) or low (voltage output) output impedance, respectively is obtained. In another embodiment each nullor has a series- coupling circuit and a parallel-coupling circuit at the output port. As a result an accurately defined or characteristic output impedance is obtained at the amplifier, and a current or voltage related both to the output current and voltage is fed to the input port, so that a low (current input) or high (voltage input) input impedance, respectively is obtained.