| 摘要 |
PURPOSE:To set a correct signal level and to always stabilize an output signal by providing a feedback circuit consisting of an automatic gain control coefficient generating circuit and a signal level setting circuit, and a DC offset compensating circuit, and eliminating a DC offset mixed in a digital signal. CONSTITUTION:When a correct digital signal D is supplied to a signal level setting circuit 22, the signal D is turned back with regard to a contact potential O, its absolute value is taken, and its signal level Vp is outputted. This signal level Vp is supplied to the third adder 215, a difference Vth-Vp to a reference value Vth from its input terminal is outputted, also a constant (k) from its input terminal is multiplied by the first multiplier 214, k(Vth-Vp) is supplied to the second adder 213, and a cumulative value of (Vth-Vp) before the previous time accumulated in the first integrator 212 is added. Accordingly, in the first adder 211, an initial value 1.0 from its input terminal is further added, a prescribed automatic gain coefficient is generated, ant it is multiplied to the input signal D which has eliminated a DC offset of the next time, by a multiplier 1. |
