| 摘要 |
PURPOSE:To obtain an inexpensive product with less power consumption by using a control signal applied to a gate of a semiconductor switching circuit to select whether the frequency characteristic of the amplification factor of an amplifier circuit is made flat or de-emphasis is applied. CONSTITUTION:An input signal Ei is amplified by an amplifier 2 and outputted (3). Resistors Rf, R are connected in series between an output terminal and common and a connecting point is connected to an inverting input of an amplifier 2. A resistor R1 and a capacitor C1 are connected in series and a series circuit comprising a resistor R2, a capacitor C2, a collector and an emitter of a transistor (TR)15 is connected in parallel with a resistor R. When a signal of L level is outputted from a de-emphasis control circuit 12 to turn off the TR15, no current flows to the resistor R2 and the capacitor C2 and the resistor R1 and the capacitor C1 show a de-emphasis characteristic, and when a signal of H level is outputted from the control circuit 12, the TR15 is turned on, a current flows also to the resistor R2 and the capacitor C2 and the output shows a flat frequency characteristic. Thus, the de-emphasis is selected simply. |
