“When it comes to communication systems, differential circuits always provide better performance than single-ended circuits-they have higher linearity, resistance to common mode interference signals, and so on. Today we will talk about the four major advantages of differential circuits in RF signal chain applications.

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When it comes to communication systems, differential circuits always provide better performance than single-ended circuits-they have higher linearity, resistance to common mode interference signals, and so on. Today we will talk about the four major advantages of differential circuits in RF signal chain applications.

1. Using differential circuits can achieve higher signal amplitudes than single-ended circuits. Under the same power supply voltage, differential signals can provide twice the amplitude of single-ended signals, and it can also provide better linearity and SNR performance.

Figure 1: Differential output amplitude

2. The differential circuit has good immunity to external EMI and crosstalk of nearby signals. This is because the received useful signal voltage is doubled, and the effect of noise on tightly coupled traces is theoretically the same, and they cancel each other out.

3. EMI generated by differential signals is often low

This is because changes in signal level (dV/dt or dI/dt) produce opposite magnetic fields, which cancel each other out again.

4. Differential signal can suppress even-order harmonics

The following shows an example of continuous wave (CW) passing through a gain block.

When using a single-ended amplifier, as shown in Figure 2, the output can be expressed as Equation 1 and Equation 2.

Figure 2: Single-ended amplifier

When a differential amplifier is used, the input and output are shown in Figure 3, expressed as Equation 3, Equation 4, Equation 5, and Equation 6.

Figure 3: Differential amplifier

Ideally, the output does not have any even-order harmonics, making differential circuits a better choice for communication systems. In fact, the biggest challenge in using differential circuits is to put aside the idea that they are difficult to design, test, and calibrate. You need to carefully observe how to use differential filters.

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