TS615

Increasing the Line Level Using Active Impedance Matching

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11 Increasing the Line Level Using Active Impedance Matching

With passive matching, the output signal amplitude of the driver must be twice the amplitude on the load.

To go beyond this limitation an active matching impedance can be used. With this technique, it is possible

to maintain good impedance matching with an amplitude on the load higher than half of the output driver

amplitude. This concept is shown in Figure 73 for a differential line.

Component calculation

Let us consider the equivalent circuit for a single-ended configuration, as shown in Figure 74.

Figure 73. TS615 as a differential line driver with active impedance matching

Figure 74. Single-ended equivalent circuit

R4

R2

Vi

Vi

Vo

Vo

RL

100

Ω

1:n

Hybrid

&

Transformer

GND

Vcc+

10

µ

100n

100n

100n

1k

1k

Rs1

Rs2

10n

1

µ

R3

R5

Vo°

Vo°

GND

Vcc+

Vcc+

+

_

+

_

GND

1/2

R1

1/2

R1

Vcc/2

1/2RL

1/2R1

R2

R3

+

_

Vi

Vo

Rs1

-1

Vo°

1/2RL

1/2R1

R2

R3

+

_

Vi

Vo

Rs1

-1

Vo°