An electrocardiogram (ECG) amplifier is an electronic component that converts relatively weak electrical signals from the heart to signals that can be output to a monitoring system. Electrodes on the body are typically where the signals are picked up first. A buffer amplifier then processes the signals and can amplify them up to ten times; ECG machines often have a differential pre-amplifier that can further enhance the electrical signal up to 100 times more. In addition to an ECG amplifier, heart monitoring machines generally consist of several components, which can include diodes, capacitors, and other parts on a circuit board.
Operational amplifiers are often used in such machines. They can reject direct current and high frequency noise interference. Various other electronic filters are often used to prevent interference from televisions and other electronic devices. An ECG amplifier can be built into a circuit along with the electronic filters and a gain stage, which typically amplifies the useful direct current.
The ECG amplifier can be built into an electrocardiogram, or the signal amplifier can be a separate component. Some versions can record data from humans and animals, in addition to isolated organs, and be set to measure different electrical signals. Most ECG amplifier types are separated from the main power circuits, because any crossover could cause a surge leading to an electrical shock. An optical isolator is often used to prevent such a problem from occurring. Typically built into the power circuit, the primary amplifier generates a current that can be used for an output.
Some ECG machines use a paper-strip recorder to display the readings. Other types transfer data to a computer, magnetic tape, or an oscilloscope that can display the activity of electrical signals. The data are usually converted to a digital format before being transferred to an output device. An ECG, therefore, generally includes an analog-to-digital converter in addition to an amplifier.
Three types of signals from the heart can be processed through an ECG amplifier. The first one is from the pacemaker, or sinoatrial node of the heart. A second signal comes from the atria, or chamber where blood enters the heart, and ventricle, which contracts to push blood out of the heart. An electrical signal representing the non-contracting phase of the ventricle is the third component of an ECG reading. With the signal amplified, physicians can read each pulse as a wave, which can be used to diagnose medical conditions such as heart damage and high blood pressure.