| 摘要 |
PROBLEM TO BE SOLVED: To make a high pass filter into an integrated circuit by multiplying a value depending on an emitter-resistance of a transistor(TR) and an on- resistance of a diode with a time constant consisting of a resistor and a capacitor so as to select a cut-off frequency thereby eliminating the need for an external element. SOLUTION: A cut-off frequency is obtained by multiplying a constant depending on resistance of 1st and 2nd resistors 2, 7, an on-resistance of 1st to 4th diodes 4, 5, 14, 15, and an emitter-resistance of transistors(TRs) 16a, 16b, 116a, 116b with a time constant depending on 3rd and 4th resistors 9, 12 and a capacitor 17. For example, in the case of setting the cut-off frequency of be 2.2kHz, the capacitance of the capacitor 17 is 100pF, the resistance of the 3rd, 4th resistors 14, 15 is 20KΩlet the resistance of the 1st resistor 2 be 40KΩ, the resistance of the 2nd resistor 7 be 20KΩ, the on-resistance of the 1st and 2nd didoes 4, 5 be 360Ω, the emitter-resistance of the TRs 6a, b be 26KΩ, the on-resistance of the 3rd and 4th didoes 4, 5 be 360Ω, and the emitter- resistance of the TRs 16a, b be 26KΩ, then the components of the 1st to 4th resistors 2, 7, 9, 12 and the capacitor 12 are integrated in an IC and no externally mounted component is required.
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