| 摘要 |
A square wave to sine wave converter using a low-pass filter. The cut-off frequency of the filter is variable in accordance with the frequency of the square wave applied to it. This is achieved by the effective value of a frequency-determining impedance in the filter varying with the square wave frequency. A resistor is switched in and out of circuit at a rate which is at least a multiple of 100 of the square wave frequency.
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