LTC1407ACMSE datasheet(12/24 Pages) LINER

12 / 24 page

LTC1407/LTC1407A

1407f

LT1818/LT1819: 400MHz, 2500V/

µs, 9mA, Single/Dual

Voltage Mode Operational Amplifier.

LT6200: 165MHz GBWP, –85dBc distortion at 1MHz,

unity gain stable, rail-to-rail in and out, 15mA/amplifier,

0.95nV/

√Hz.

LT6203: 100MHz GBWP, –80dBc distortion at 1MHz,

unity gain stable, rail-to-rail in and out, 3mA/amplifier,

1.9nV/

√Hz.

LT6600: Amplifier/Filter Differential In/Out with 10MHz

Cutoff.

INPUT FILTERING AND SOURCE IMPEDANCE

The noise and the distortion of the input amplifier and

other circuitry must be considered since they will add to

the LTC1407/LTC1407A noise and distortion. The small-

signal bandwidth of the sample-and-hold circuit is 50MHz.

Any noise or distortion products that are present at the

analog inputs will be summed over this entire bandwidth.

Noisy input circuitry should be filtered prior to the analog

APPLICATIO S I FOR ATIO

inputs to minimize noise. A simple 1-pole RC filter is suf-

ficient for many applications. For example, Figure 1 shows

a 47pF capacitor from CHO+ to ground and a 51

Ω source

resistor to limit the net input bandwidth to 30MHz. The

47pF capacitor also acts as a charge reservoir for the input

sample-and-hold and isolates the ADC input from sam-

pling-glitch sensitive circuitry. High quality capacitors and

resistors should be used since these components can add

distortion. NPO and silvermica type dielectric capacitors

have excellent linearity. Carbon surface mount resistors

can generate distortion from self heating and from dam-

age that may occur during soldering. Metal film surface

mount resistors are much less susceptible to both prob-

lems. When high amplitude unwanted signals are close in

frequency to the desired signal frequency a multiple pole

filter is required.

High external source resistance, combined with 13pF of

input capacitance, will reduce the rated 50MHz input band-

width and increase acquisition time beyond 39ns.

Figure 1. RC Input Filter

LTC1407/

LTC1407A

CH0+

CH0–

VREF

GND

1407 F01

µF

47pF*

Ω*

CH1+

CH1–

47pF*

*TIGHT TOLERANCE REQUIRED TO AVOID

APERTURE SKEW DEGRADATION

Ω*

ANALOG

INPUT

ANALOG

INPUT

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