| 摘要 |
PURPOSE:To reduce heat dissipation of a speech current supply circuit and to eliminate noise superimposed onto a DC current by not supplying directly a DC current to an electronic circuit but supplying the current via a noiseless DC voltage generating circuit. CONSTITUTION:A noiseless DC voltage generating circuit 3 receives a DC voltage from a DC power supply VB and an AC noise voltage included in the DC power supply VB is connected to a filter circuit comprising of a series circuit of resistors R2D, R3D via a resistor R1D and a capacitor CD connected in parallel with the series circuit and is led to the ground. Thus, only the DC voltage without noise is inputted to operational amplifiers OPD, OPE. Since the operational amplifiers OPD, OPE act like amplifiers whose amplification factor is the unity, the same DC voltage as the input voltage is fed to resistors RED, R2A of an electronic circuit 1a. Thus, a DC current without noise to the terminal equipment is sent. Moreover, since the speech current is decreased, the heat dissipation in the speech current supply circuit is reduced. |
