The difference between differential output and single-ended output

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The difference between differential output and single-ended output

Posted Date: 2024-02-01

The difference between differential output and single-ended output

Differential output

Differential output is a circuit design technology that is mainly used to extract signal changes, amplify and process signals. Differential output amplifies the input signal through a differential amplifier and then outputs two signals with opposite phases.

This method has the characteristics of high common mode rejection ratio and strong noise suppression capability, which can reduce the impact of interference on the output signal. The basic principle of the differential output method is to extract useful information by comparing the difference between two input signals.

The differential input signal is amplified by a differential amplifier and forms a differential output signal. This design method can suppress common mode noise and amplify signal differences, thereby improving signal effectiveness.

Differential outputs offer several advantages in circuit design. First, it can improve signal accuracy and remove common error interference. In differential input, the difference between the two input terminals is used as the signal, which can avoid some errors, such as power supply deviation, line impedance mismatch, etc. Second, the differential output is highly immune to external electromagnetic interference (EMI).

An interferer affects each end of a differential signal pair almost equally. Since the voltage difference determines the signal value, this will ignore any identical interference occurring on both conductors. In addition to being less sensitive to interference, differential signals generate less EMI than single-ended signals. In addition, the differential output handles "bipolar" signals with ease and precision. In a single-supply system, "bipolar" signals can be handled by correctly distributing the virtual ground.

All circuits require a complete current loop to function properly. For single-ended circuits, the signal is transmitted to the receiver through a single wire. The signal is the level difference between the signal transmitted by one wire and ground. This The disadvantage of this solution is that if there is noise on the ground plane, it will affect all circuits linked to it. Differential signaling uses two wires or PCB traces.

The second wire or trace provides a loop for the current, which is 180 degrees out of phase with the signal on the wire (i.e., the complementary signal) relative to the real signal. Unlike single-ended signal transmission, the loop of the differential signal is specifically designed for this purpose. circuit.

How differential output works:

1. Differential generator: The differential generator is the key component for generating differential output signals. It usually consists of a crystal oscillator or oscillator circuit driving a differential amplifier. The crystal oscillator or oscillator circuit provides an input signal to the differential amplifier, and then the amplifier generates two signals, positive phase and negative phase. The positive phase signal and the negative phase signal have the same voltage amplitude but opposite polarity.

2. Differential transmission lines: Differential transmission lines are used to transmit differential output signals from the generator to the receiver. A differential transmission line usually consists of a pair of wires arranged in parallel, one carrying a positive-phase signal and the other carrying an anti-phase signal. Since the two signals remain balanced with each other during transmission, signal interference and transmission loss can be reduced.

3. Differential Receiver: A differential receiver is used to receive and decode the differential output signal and convert it into a single-ended signal for subsequent circuit use. A differential receiver consists of two inputs and an output. At the receiving end, after differential amplification and differential decoding of the forward-phase signal and the reverse-phase signal, a decoded single-ended signal is obtained.

The advantage of differential output lies in its strong ability to resist transmission line noise and interference. The difference between forward and reverse phase signals can be used to eliminate common mode noise and suppress interfering signals. In addition, differential output can also improve the signal's anti-interference ability and signal integrity.

Review Editor: Huang Fei

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