| 摘要 |
PURPOSE:To improve the linearity of a dynamic range, by applying a prescribed bias to the 2nd gate of an FET constituting an AGC circuit element, dividing the voltage between the drain and the source to feed the corresponding divided voltage back to the 1st gate. CONSTITUTION:An input signal is supplied through a terminal 1 and amplified by a transistor 8 which forms an AGC amplifier 2' to be delivered through an output terminal 3 after passing through a capacitor C2. A part of the output voltage receives a wave detection by a wave detector 4', and this detected voltage is fed to the 2nd gate G2 of an FET7 to control the FET7. The voltage obtained by dividing the drain voltage is fed back to the 1st gate of the FET7. At the same time, the detected voltage is fed to the emitter of the transistor 8 from a terminal 10 via the FET7 having good noise characteristics and the a capacitor C3 of a main amplifer 2'. As a result, the gain of the amplifier 2' is controlled at a certain level. |
