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Time (2ns/div)

Output

Input

2.0

1.5

1.0

0.5

0

-0.5

-1.0

-1.5

G048

High-Speed Full-Wave Rectifier

High-Speed Full-Wave Rectifier #1

V

H

V

L

V

O

402

Ω

402

Ω

500

Ω

200

Ω

50

Ω

Source

57.2

Ω

OPA698

S0041-01

OPA698M

SGLS287A – MAY 2005 – REVISED MARCH 2006

TYPICAL APPLICATIONS (continued)

Figure 54. 100-MHz Sine Wave Rectified

There are two methods shown here to build a high-speed full-wave rectifier with a limiting amplifier: use the

half-wave rectifier described previously with another amplifier to obtain the full-wave rectified, or use the input to

set the limiting voltage.

The circuit shown in Figure 55 uses only one amplifier, in an inverting gain of –1 configuration. The upper limiting

voltage is left open, resulting in an upper limiting voltage of +3.5 V. The lower limiting voltage is connected to the

input signal, resulting in the following behavior. When the input voltage is negative, the amplifier is not limiting,

resulting in the inversion of the input sine wave to the output. During the positive excursion of the input signal,

the output signal is being driven by the limiting input pin. Since the output is driven from the limiter input pin from

positive inputs, the lower slew rate in the input path restricts the application of this approach to lower amplitude

and/or frequencies. A 2-MHz fully rectified sine wave is shown in Figure 56.

In order to reach higher frequencies, a second method is recommended.

Figure 55. High-Speed Full-Wave Rectifier #1

18

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