CLC451 datasheet(11/12 Pages) NSC

11 / 12 page

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Twisted Pair Driver

The high output current and low distortion, of the

CLC451, make it well suited for driving transformers.

Figure 13 illustrates a typical twisted pair driver utilizing

the CLC451 and a transformer. The transformer

provides the signal and its inversion for the twisted pair.

Figure 13: Twisted Pair Driver

To match the line’s characteristic impedance (Zo) set:

RL = Zo

Rm = Req

Where Req is the transformed value of the load imped-

ance, (RL), and is approximated by:

Select the transformer so that it loads the line with a

value close to Zo, over the desired frequency range. The

output impedance, Ro, of the CLC451 varies with

frequency and can also affect the return loss. The return

loss, shown below, takes into account an ideal

transformer and the value of Ro.

The load current (IL) and voltage (Vo) are related to the

CLC451’s maximum output voltage and current by:

From the above current relationship, it is obvious that an

amplifier with high output drive capability is required.

Return Loss(dB)

20log

≈−

⋅

Vn V

max

≤⋅

≤

UTP

Req

1:n

V = Av Vin

v in

-n

v in

ov in

Vin

CLC451

Ω

0.1

µF

6.8

µF

VEE

Av = 2

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