| 摘要 |
PURPOSE:To improve the frequency characteristic of an amplifier at a low frequency region with simple circuit constitution by devising a feedback circuit in a multi-stage feedback amplifier. CONSTITUTION:Negative feedback impedances 16, 17 consist of elements passing a DC component. An input signal at a terminal 14 is outputted from a terminal 15 via an FET1, a capacitor 3 and an FET2. An impedance 16 is provided between both gates G of the FET1 and FET2 being of equi-potential as a feedback impedance of the 1st stage. Furthermore, in selecting a device barometer of the FETs 1, 2 and load impedances 4, 5, since both the drains D of the FETs 1, 2 are made equi-potential, when an impedance 17 is provided between them as a feedback circuit of the 2nd stage, a feedback amplifier circuit having no DC cut- off capacitor is constituted in the feedback loop. Thus, the number of capacitors is halved or more than that of a conventional circuit and the constitution is simplified and the frequency characteristic at a low frequency region is improved.
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