EL2003C データシートの表示（PDF） - Elantec -> Intersil

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EL2003C

100MHz Video Line Driver

Elantec -> Intersil 

EL2003C, EL2033C

100MHz Video Line Driver

impedance of the EL2003C or EL2033C is less than

10Ω from DC to about 10MHz, but a capacitive load of

1000pF will generate about 45° phase shift at 10MHz

and make high speed op amps unstable. Obviously more

capacitance will cause the same problem but at lower

frequencies, and slower op amps as well would become

unstable.

The easiest way to drive capacitive loads is to isolate

them from the feedback with a series resistor. Ten to

twenty ohms is usually enough but the final value

depends on the op amp used and the range of load

capacitance.

If the system requirements will not tolerate the isolation

resistor, then additional high frequency feedback from

the op amp output (the buffer input) and an isolating

resistor from the buffer output is required. This requires

that the op amp be unity gain stable.

Complex Feedback with the Buffer to Drive Capacitive Loads

This works with any unity gain stable OA.

Snubber Circuit (51Ω 470 pF) is optional.

Op Amp Booster with Capacitive Load

10Ω is enough isolation and speed

is determined by the isolation

CL

tr

OS

resistor and capacitive load time

10pF

17ns

10%

constant.

470pF

20ns

50%

0.001µF

30ns

35%

0.005µF

80ns

0

0.01µF

220ns

0

0.05µF

1.1µs

0

0.1µF

2.2µs

0

11

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