| 摘要 |
PROBLEM TO BE SOLVED: To amplify a reproduced signal with a wide band and sufficient S/N by amplifying an output reproduced signal of a rotary transformer using a current feedback type operational amplifier circuit, and reducing input impedance by increasing quantity of negative feedback. SOLUTION: Resistors R11, R12 are set to, for example, 2.2Ω, 330Ωrespectively at a secondary output side of a rotary transformer T1, and resistors R14, R15 are set to, for example, 220Ω, 100Ωrespectively. Then, a DC operation point is set in an operational amplifier circuit 11, also, sufficient DC feedback quantity is given. Capacitors C11, C12 are set to, for example, 100μF, 0.1μF. Then, AC feedback quantity being sufficient even in a low frequency is given to the operational amplifier circuit 11 through the capacitor C11, also the capacitor C12 is operated in parallel with the resistor R14 and forms a low pass filter in an AC feedback loop. The operational amplifier circuit 11 outputs a reproduced signal RF through a resistor R16 of 100Ω.
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