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TIPD111: Strange signal on the slope detection output

Part Number: TIPD111


I did the Pace detection as mentionned in the TIPD111. Instead of 5V, I supplied the circuit to 3.3V.

This circuit is connected the PACE_OUT ADS1294R chipset.

I attached a scope where the channel 1 is ECG+Pace and channel 2 is the voltage at the OPA348.

With the whaletek tool, I can manage the Pace pulse voltage and duration.

Due to the strange singl on the Channel 2, I am not able to detect PACE level below 50mV.

I used exactly the same value mentionned in document.

Do you have an idea about the strange signal seen on channel2?

Due to the starnge signal on the OPA348 output signal, I can't decrease the pace level until 2mV. How to clean this?




  • Hi Damien,

    Thanks for your post. Please accept delayed response as many of us are on holiday break. We will support you shortly.


  • Hi Damien,

    the output signal of OPA348 looks more like an amplified and inverted copy of the input signal, as if the OPA348 would work as an inverter with a bit of gain.

    Are you sure that your signal generator has a 0R source impedance? Only then the OPA348 will work as true differentiator.

    Also, increase the supply voltage to 5V for a test.