A sine-cosine generator

Posted on Dec 15, 2012

The scheme presented delivers waveforms from any function generator producing a triangular output and a synchronized TTL square wave. A1 and A2 act as a two-phase current fectifier by inverting the negative voltage appearing at the input of Al. Positive input: Both Al and A2 work as unity gain followers,D1 and D2 being in the off-state. Negative input: Al has a - 2/s gain (D1 off and D2 on), A2 has a + Vi gain and the total voltage transfer is -1 between output and input. PI allows a fine trimming of the -1 gain for the negative input signals. A3 adds a continuous voltage to the rectified positive signal in order to attack A4 which acts as a ± multiplier commanded by the TTL input through the analog switch.

A sine-cosine generator
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The signal polarity is reconstructed and the output of A4 delivers a triangular waveform shifted by 90° with respect to the input signal, Fig. 2. The original and the shifted voltages are fed into the triangle to sine converters through A5 and A7 working as impedance converters. Over the frequency dynamic ranges from 0.1 Hz to 10 kHz, the phase shift is constant and the distortion on the sine voltage is less than 1%.

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