| 摘要 |
PROBLEM TO BE SOLVED: To provide an attenuator small in size, small in frequency characteristic and easy in design by controlling the on-state and off-state of FETs thereby changing over a passing circuit and aπ-connection attenuator. SOLUTION: With a 1st field effect transistor (FET) 1 and a 2nd FET 2 set open and with a 3rd FET set closed, the 1st FET 1 and the 2nd FET 2 are open to an input terminal 6a and an output terminal 6b, and let the resistance of the 3rd FET 3 be selected small, then the equivalent circuit of the attenuator indicates a passing circuit. With the FET 1 and the 2nd FET 2 set closed and with the 3rd FET 3 set open, let the resistance of the 1st FET 1 and the 2nd FET 2 be selected small, and let the 3rd FET 3 be open, that is, the impedance of the 3rd FET 3 is very high. The equivalent circuit indicates aπ-connection attenuator consisting of 1st resistor 4a-3rd resistor 4c.
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