| 摘要 |
PURPOSE:To prevent the drift of differential amplifying circuit from being taken place, by making equal the DC potential of non-inverting and inverting input, in the direct coupling amplifier performing non-inversion amplification providing the differential amplifying circuit. CONSTITUTION:The signal path of the direct coupling amplifier A is constituted with the input stage 1 consisting of differential amplifier having FETQ1, Q2, exciting stage 2 having the bipolar transister TRQ3, and output stage 3 having TrQ4, Q5. The DC potential of the gate of Q1 being the non-inverting terminal is detected with the resistor 20 and the capacitor 21, and the output is converted into rectangular wave with TRQo to which the rectangular wave signal is applied and it is DC signal with smoothing of capacitor C2s via the AC amplifier 23 and the synchronous linear detector TRQ7. This output is divided with the resistors 18 and 26 and is fed to the gate of Q2 being the inverting input. When the amplifier of the amplifier 23 or the resistor 26 is adjusted and the DC potential of the gate 7 of Q1, Q2 is made equal, then the drift of the differential amplifier can be prevented. |
