| 摘要 |
PURPOSE:To improve the function of a device and to prevent the area from increasing at the time of LSI-implementation by varying the output pattern of a decoder, e.g. a pattern for controlling analog switches with a control signal and switching the quantities of attenuation and the numbers of steps which are varied through an up switch and a down switch. CONSTITUTION:A resistance 13 is connected to the input terminal of each analog switch 14. Analog switches 14 are controlled with outputs D1...Dn+1 of the decoder 19 which decodes the output of an up-down counter 18 which counts up or down through the operation of the up switch 16 or down switch 17. Then, the up/down counter 18 has (2n+1) count capacities and when a control signal CONT is '0', the decoder 19 outputs one output in the order of the outputs D1...Dn+1 or in the opposite order every time the up/down counter 18 counts up or down by one. When the control signal CONT is '1', on the other hand, one and two outputs are sent out alternately in the order of D1, D1 and D2, D2, D2+D3, D3...Dn or in the opposite order.
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