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OPA698

V

O

R

S

V

S

R

F

24.9

Ω

R

C

S0045-01

DC Restorer

OPA698

V

O

75

Ω

Load

8

5

V

L

V

402

Ω

R

2

1k

Ω

R

3

200

Ω

D

1

402

Ω

20

Ω

V

IN

200

Ω

75

Ω

R

Q

250

Ω

R

1

19.6k

Ω

D

2

C

1

20

µF

6

1

C

E

B

3

CCII

2

U1

5

+1

U1

U1 = OPA660

R

D

S0047-01

Video Sync Stripper

OPA698M

SGLS287A – MAY 2005 – REVISED MARCH 2006

TYPICAL APPLICATIONS (continued)

Figure 63. Unity-Gain Buffer

Figure 64 shows a dc-restore circuit using the OPA698 and OPA660. The buffer element of the OPA660 is used

to buffer the input signal, while the transconductance element is used to restore the dc level after the decoupling

capacitor C1. The dc level is set using R1 and R2. The OPA698 is configured at a gain of two to compensate for

the 75-

Ω series into a 75-Ω load. The OPA698 also limits the output to ground.

Figure 64. DC Restore to Ground

Figure 65 shows a sync stripper using two OPA698 output-limiting op amps. One OPA698 is configured as a

limiting inverting comparator. Referring to the input, the negative excursions lower than –0.2 V are clipped to

ground and all excursions greater than –0.2 V generate an output voltage set by the default limiting value (–3.5

V). The second OPA698 is using this waveform to effectively remove the sync pulse from the video signal.

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