| 摘要 |
PURPOSE:To widen the dynamic range, by applying an input signal to an amplifying element via a capacitor and a diode, and changing an impedance between the input side of the diode and the reference potential in accordance with an output signal level. CONSTITUTION:When a control transistor (TR) 17 is turned off at a weak input, a bias current flows to a variable attenuation diode 19 via a bias resistor, the impedance of the diode 19 is reduced and an input signal is applied to an amplifying FET6 directly. Since the TR17 is at off-state, no signal component is attenuated. When the TR17 turns on at a strong input, a bias current flows to the TR17 and the impedance of the diode 19 is increased, and since the signal component is by-passed to ground via the TR17, the signal component applied to the gate of the FET6 is attenuated. |
