Apparatus for processing biomedical signals for display
Apparatus and methods remove a voltage offset from an electrical signal, specifically a biomedical signal. A signal is received at a first operational amplifier and is amplified by a gain. An amplitude of the signal is monitored, by a first pair of diode stages coupled to an output of the first operational amplifier, for the voltage offset. The amplitude of the signal is then attenuated by the first pair of diode stages and a plurality of timing banks. The attenuating includes limiting charging, by the first pair of diode stages, of the plurality of timing banks and setting a time constant based on the charging. The attenuating removes the voltage offset persisting at a threshold for a duration of at least the time constant. Saturation of the signal is limited to a saturation recovery time while the saturated signal is gradually pulled into monitoring range over the saturation recovery time.
1. A system for displaying electrocardiogram (ECG) and intracardiac (IC) signals, comprising:
a plurality of inputs configured to receive electrophysiological signals, the electrophysiological signals comprising first signals from a catheter when disposed inside a heart of a patient and second signals from at least three limb electrodes, when each limb electrode is disposed on a respective different limb of the patient;
a differential amplifier stage coupled to the plurality of inputs and configured to output a differential signal representing electrophysiological activity;
a right-leg drive (RLD) circuit electrically coupled to the at least three limb electrodes and configured to output a RLD output signal to a right-leg electrode when located on the patient's right leg;
an analog-to-digital converter module configured to convert the differential signal representing electrophysiological activity to a digitized electrophysiological signal; and
one or more processors configured to format the digitized electrophysiological signal to be at least one of displayed on a display unit and stored.
2. The system of claim 1 , wherein the RLD circuit is configured to remove a common mode voltage from the second signals received from the at least three limb electrodes.
3. The system of claim 1 , wherein the RLD circuit has a common mode configured to reject power line noise at a first harmonic frequency and a third harmonic frequency.
4. The system of claim 1 , wherein the RLD circuit is configured to prevent current having an amplitude greater than one microampere from flowing to the right-leg electrode.
5. The system of claim 1 , wherein the at least three limb electrodes comprise a right-arm electrode, a left-arm electrode, and a left-leg electrode.
6. The system of claim 3 , wherein the first harmonic frequency is 60 Hz and the third harmonic frequency is 180 Hz.
7. The system of claim 3 , wherein the RLD circuit is further configured to combine the second signal from the at least three limb electrodes by averaging the electrophysiological signals from the right-arm electrode, the left-arm electrode, and the left-leg electrode.