NJM2211 FSK demodulator problem.

Hi guys,
I tried to build this 1200 baud fsk decoding circuit using this NJM2211 ( the exact circuitary is given in the chip manual -> https://picbasic.com/downloads/NJM2211.pdf) I used the recommand component values fsk decoding too.

I tested the circuit with both a 1.2kHz 1Vpp input and 2.2kHz input, the output at pin 7 was always at 4.x VDC....Shouldn't the output be at "LOW" when my input frequency's at 2.2kHz ?

I wonder why this is happening. Please help =)

* Oh another thing, I set V+ = around +5VDC when i was testing the chip.

Your link did not work for me. Go to this link and click on "data sheet". **broken link removed**

Did you use the values given in table 1, including the trim pot?

Yes, I used the values from table 1 and configured that circuit as given in figure 2. I did use a 5K trim pot as Rx.
Though, I'm not sure if I connected the trim pot correctly.

For the trim pot, there was 3 pins and I only used two of them ( I tested these two pins with a multimeter and the resistance was variable ) and i left the third pin open.

i'm sorry for any misused words ...I'm not really familiar with these stuffs.

and ~ Thanks for the help = )

Anyone ever used this chip before? Please help.

s3art said:

Anyone ever used this chip before? Please help.

Click to expand...

I haven't used it, but I noticed that pin 4, according to the pinout on p.1, should be connected to GND. This isn't shown in Fig. 2.

HA!..pin4 to GND ....that solved my problem ..
thanks all.