| 摘要 |
PURPOSE:To obtain a product having always uniform characteristic by adopting the constitution so that the current of the 2nd transistor (TR) provided to the pre-stage of the 3rd TR for feedback may be varied to change the frequency characteristic thereby setting the overall frequency characteristic optionally. CONSTITUTION:The 1st TR 11 receiving an output of a photocoupler, the 2nd TR 13 receiving an output of the 1st TR 11 and the 3rd TR 21 feeding back the output of the 2nd TR 13 to the 1st TR via a resistor 16 are provided and the current flowing to the 2nd TR 13 is varied to change the frequency characteristic. A current flows to the 3rd TR 21 so that the entire frequency characteristic is nearly flat. Thus, the necessity of use of a capacitor is eliminated, the circuit integration and its adjustment are facilitated and a product having the always uniform characteristic is attained.
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