| 摘要 |
PURPOSE:To prevent the deterioration of frequency characteristics of a preamplifier and oscillation and to achieve the preamplifier suitable for circuit integration, by incorporating a ground line of the preamplifier and that of a signal processing circuit provided at the post stage of it, so that the reproduced signal such as a magnetic recorder/reproducer and the like can not flow to a ground terminal. CONSTITUTION:A preamplifier 21 consists of a transistor TRQ21, the base of which is connected to one terminal of a transformer T21 induced with an input (reproduced) signal Vi and the emitter of which is connected to another terminal of the transformer T21 via a capacitor C21, and a resistor R22 inserted between the emitter of the TRQ21 and ground, and a base bias circuit consisting of a base bias power supply E21 and resistor R23 is provided between the transformer T21 and ground. The signal Vi is picked up from the collector of the TRQ21 and an output VO is taken via TRs Q22, Q23 and it is applied to a signal processing circuit provided at the post stage. Thus, the signal Vi does not pass through a ground terminal 3, the signal Vi is not affected even if the operating current of the signal processing circuit flows to the terminal 3. |
