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8

Document Number: 70057

S11-0154-Rev. I, 31-Jan-11

Vishay Siliconix

DG611, DG612, DG613

TEST CIRCUITS

APPLICATIONS

High-Speed Sample-and-Hold

In a fast sample-and-hold application, the analog switch

characteristics are critical. A fast switch reduces aperture

uncertainty. A low charge injection eliminates offset (step)

errors. A low leakage reduces droop errors. The CLC111, a

fast input buffer, helps to shorten acquisition and settling

times. A low leakage, low dielectric absorption hold capacitor

must

be

used.

Polycarbonate,

polystyrene

and

polypropylene are good choices. The JFET output buffer

reduces droop due to its low input bias current.

(see figure 5.)

Pixel-Rate Switch

Windows, picture-in-picture, title overlays are economically

generated using a high-speed analog switch such as the

DG613. For this application the two video sources must be

sync locked. The glitch-less analog switch eliminates halos.

(see figure 6.)

GaAs FET Drivers

Figure 7 illustrates a high-speed GaAs FET driver. To turn

low-power driver is especially suited for applications that

require a large number of RF switches, such as phased array

radars.

Figure 3. Charge Injection

1 nF

D

V+

S

V-

5 V

IN

- 3 V

GND

+ 15 V

+ 5 V

Figure 4. Crosstalk

1 V, 4 V

1 V, 4 V

V+

50



C = RF bypass

- 3 V

GND

V-

NC

C

+ 15 V

C

+ 5 V

C

Figure 5. High-Speed Sample-and-Hold

CLC111

75



+

-

LF356

5 V Control

Analog

Input

Input Buffer

S

IN

D

Output Buffer

± 5 V Output

to A/D

+ 5 V

+ 12 V

- 5 V

650 pF Polystyrene