| 摘要 |
PURPOSE:To ensure a free variation of the suppressing effect of noise, by adding a bias varying means to a transistor circuit for suppression of noise. CONSTITUTION:The input signal is divided into the low-and high-band components through the low-and high-pass filters 12 and 13. The low band component is applied directly to the mixer 14, and the high-band component is applied to the same mixer 14 via the noise suppressing circuit 15. The circuit 15 consists of the bias control circuit comprising the transistors 18 and 19, resistances 20 and 21 plus the variable resistance 23. The base bias voltage of the transistors 18 and 19 is varied by changing the resistance value of the resistance 23. Thus the cut-off region is varied for the transistors 18 and 19. In such way, the noise suppressed region can be varied. |
