The line has been completely unbalanced as regards talking to other lines, although its own common-mode rejection remains good.

This creates a balanced audio circuit with common-mode rejection also known as a differential pair.

The device set the direction for the industry for decades, despite poor common-mode rejection ratio, weak output drive capabilities, and a price of $300.

The common-mode rejection ratio is defined as:

The technique has something in common with what electrical engineers call common-mode rejection and is also found in balanced lines in audio recording.

The ideal op amp has infinite common-mode rejection ratio, or zero common-mode gain.

The 6.8 kΩ value is not critical, but the resistors must be matched to within 0.4% or better to maintain good common-mode rejection in the circuit.

The standard measure of this defect is called the common-mode rejection ratio (denoted CMRR).

Each board provides one differential-input channel with a common-mode rejection ratio of 96dB (typ) for maximum rejection of signal interference.

An IC instrumentation amplifier typically contains closely matched laser-trimmed resistors, and therefore offers excellent common-mode rejection.

Modern differential amplifiers can easily provide common-mode rejection ratios (CMRR) higher than 100 dB.

Common-mode rejection ratio (CMRR)

The common-mode rejection ratio (CMRR), which characterizes the performances of the cell in the presence of common noise, has been measured.

The classic four-resistor differential amplifier configuration also works with a CFA, but the common-mode rejection ratio is poorer than that from a VFA.

A 'fully-balanced' circuit has a common-mode rejection ratio of pricisely zero, since all signal, common-mode or not, is simply amplified and passed along via the two signal paths.

Additional characteristics include very low DC offset, low drift, low noise, very high open-loop gain, very high common-mode rejection ratio, and very high input impedances.

However, the fourth quadrant common-mode response data is a measure of common-mode transmission response and used in a ratio with the differential transmission response to determine the network common-mode rejection.

To maximize the common-mode rejection ratio (CMRR), differential probes must provide two signal paths that are as nearly identical as possible, matched in overall attenuation, frequency response, and time delay.

They were designed to have extremely small input current and are still amongst the best op-amps available in terms of common-mode rejection with the ability to correctly deal with hundreds of volts at their inputs.

This issue was addressed by swapping the positions of the two legs every few hundred yards with a cross-over, thus ensuring that both legs had equal interference induced and allowing common-mode rejection to do its work.

Balanced interconnection This turns the spurious noise due to ground loop current into Common-mode interference while the signal is differential, enabling them to be separated at destination, by circuits having a high common-mode rejection ratio.

This method starts to fail when the noise source is close to the signal wires; the closer wire will couple with the noise more strongly and the common-mode rejection of the receiver will fail to eliminate it.

The common-mode rejection ratio (CMRR), usually defined as the ratio between differential-mode gain and common-mode gain, indicates the ability of the amplifier to accurately cancel voltages that are common to both inputs.

Apart from generating noticeable hiss, 741s and other older op-amps may have poor common-mode rejection ratios and so will often introduce cable-borne mains hum and other common-mode interference, such as switch 'clicks', into sensitive equipment.

The common-mode rejection ratio (CMRR) of a differential amplifier (or other device) measures the ability of the device to reject common-mode signals, those that appear simultaneously and in-phase on both amplifier inputs.