Help with AD630 - schematic check

Discussion in 'The Projects Forum' started by Tehell, Jan 16, 2014.

  1. Tehell

    Thread Starter New Member

    Jan 16, 2014

    I am currently working on demodulator with AD630 but my schematic and test board seems not working. I took the schematic from AD630 datasheet, p. 10, fig.14. Schematic, which I have made is attached.

    The test board is 2 x 3 (cm). Elements are close to each other. It is powered from laboratory power supply and it has +/- 10V on pins 8 and 10.

    To the input (1) and (16) there is connected generator Philips PM5139, which generates sin with 1 kHz frequency with PSK modulation with 20 Hz freq.

    To the pin no 9 there is another generator connected, which gives me a carrer/reference sinus 1 kHz.

    After the chip I have put low-pass filter, which cuts the frequency above 1 kHz, used resistance and capacitance are following 400 Ω i 4 nF.

    At the output I have connected digital oscilloscope. I was predicting that I should see my 20 Hz signal, which was my modulation frequency. But... the only thing I can see is a noise, which has very small amplitude, almost none.

    However, after FFT I had something on 20 Hz, little peak that might be my signal. If I change the frequencies, nothing happens, I do not see any changes on the oscilloscope.

    Thank you for any clues, Teh.