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OPA521

SBOS872 – MAY 2018

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8.2.2 Detailed Design Procedure

8.2.2.1 System Examples

8.2.2.1.1

Power Amplifier Block

This power amplifier transmits data onto power lines through a line-coupling circuit. The power amplifier consists

of a high slew rate, high-voltage, and high-current operational amplifier. The amplifier is configured with an

inverting gain of 7 V/V and maintains excellent linearity and low distortion throughout the bandwidth. The

amplifier operates from 7 V to 24 V and can deliver up to ±1.9 A of continuous output current over the specified

junction temperature range of –40°C to +125°C. Connecting the amplifier in a typical power line communication

(PLC) application requires a few additional components. Figure 2 shows the typical connections to the amplifier.

Figure 2. Typical Connections to the Amplifier

8.2.2.1.1.1

+IN Connection

The +IN pin provides the correct half power supply bias for the quiescent output voltage. The +IN pin is always

connected to a DC bias equal to (V+) / 2.

8.2.2.1.1.2

-IN Connection

and amplifier combination has a band-pass response because of the inherent low-pass transfer function from the

the amplifier circuit. Equation 2 calculates this value:

where:

•

•

(2)

must be determined to withstand operation up to the PA power supply voltage.

which must always be connected to a noise-free, low-impedance source of one-half of the supply voltage (V+).

8.2.2.2

Line-Coupling Circuit

The line-coupling circuit is one of the most critical circuits in a power line modem. The line-coupling circuit blocks

the low-frequency signal of the mains (commonly 50 Hz or 60 Hz) from damaging the low-voltage modem

circuitry and couples the modem signal to and from the AC mains. Figure 3 shows a typical line-coupling circuit.