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A Driven Right Leg circuit or DRL circuit, also known as Right Leg Driving technique, is an electric circuit that is often added to biological signal amplifiers to reduce common-mode interference. Biological signal amplifiers such as ECG ( electrocardiogram ) EEG ( electroencephalogram ) or EMG circuits measure very small electrical signals ...
The amplitude of ECG ranges from 0.3 to 2 mV for the QRS complex, which is used to determine the interbeat interval from which the frequency is derived. The typical requirements for the amplifiers to be used in ECG include: [1] Low internal noise (<2 mV) High Input Impedance (Z in > 10 MΩ) Bandwidth ranging from 0.16–250 Hz
ECG voltages measured across the body are very small. This low voltage necessitates a low noise circuit, instrumentation amplifiers, and electromagnetic shielding. Simultaneous lead recordings: earlier designs recorded each lead sequentially, but current models record multiple leads simultaneously.
A commonly used amplifier is the instrumentation amplifier. Instrumentation amplifiers such as the integrated circuit (IC) AD620 amplifier are able to amplify the difference between two different voltage inputs while maintaining little offset voltage and a high CMRR, allowing it to amplify low frequency signals while rejecting noise. [31]
If circuit 2 is an audio system and circuit 1 has large AC currents flowing in it, the interference may be heard as a 50 or 60 Hz hum in the speakers. Also, both circuits have voltage on their grounded parts that may be exposed to contact, possibly presenting a shock hazard. This is true even if circuit 2 is turned off.
The group delay and phase delay properties of a linear time-invariant (LTI) system are functions of frequency, giving the time from when a frequency component of a time varying physical quantity—for example a voltage signal—appears at the LTI system input, to the time when a copy of that same frequency component—perhaps of a different physical phenomenon—appears at the LTI system output.
The bootstrap circuit uses a coupling capacitor, formed from the gate/source capacitance of a transistor, to drive a signal line to slightly greater than the supply voltage. [10] Some all-pMOS integrated circuits such as the Intel 4004 and the Intel 8008 use that 2-transistor "bootstrap load" circuit. [11] [12] [13]
Paul Voigt patented a negative feedback amplifier in January 1924, though his theory lacked detail. [4] Harold Stephen Black independently invented the negative-feedback amplifier while he was a passenger on the Lackawanna Ferry (from Hoboken Terminal to Manhattan) on his way to work at Bell Laboratories (located in Manhattan instead of New Jersey in 1927) on August 2, 1927 [5] (US Patent ...