| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a meter drive circuit that can match the swing of a needle of an audio level meter with the volume that people hear. <P>SOLUTION: The meter drive circuit for driving the needle type audio level meter includes a logarithmic circuit 18 for logarithmically converting an audio signal. The logarithmic circuit 18 includes operational amplifiers 181, 182, transistors 183, 184 and resistances 186, 187. The transistor 183 has a base grounded, an emitter connected to an output terminal of the operational amplifier 181 via the transistor 184 and the resistance 186, and a collector connected to an inverting input terminal of the operational amplifier 181. The transistor 184 has a base connected to the resistances 186, 187, an emitter connected to the emitter of the transistor 183, and a collector connected to an inverting input terminal of the operational amplifier 182. The emitters of the transistors 183, 184 are connected to an output terminal of the operational amplifier 182. <P>COPYRIGHT: (C)2012,JPO&INPIT |
