MAX3864 データシートの表示（PDF） - Maxim Integrated

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MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range Transimpedance Preamplifier

Maxim Integrated 

2.5Gbps, +3V to +5.5V, Wide Dynamic Range

Transimpedance Preamplifier

MAX3864

RF = 1kΩ

VOLTAGE

OUTPUT

OUTPUT

TRANSIMPEDANCE AMPLIFIER

AMPLIFIER

BUFFER 50Ω

FILTER

IN

OUT+

OUT-

50Ω

LOWPASS FILTER

VCC

VCC

GND

DISABLE

DC CANCELLATION

750Ω

CIRCUIT

FILTER

Figure 1. Functional Diagram

AMPLITUDE

AMPLITUDE

INPUT FROM PHOTODIODE

TIME

OUTPUT (SMALL SIGNALS)

OUTPUT (LARGE SIGNALS)

Figure 2. Limited Output

For optimum supply-noise rejection, the MAX3864

should be terminated with a differential load. If a single-

ended output is required, the unused output should be

terminated with 50Ω to VCC. The MAX3864 will not drive

a DC-coupled, 50Ω grounded load.

Output Filter

The MAX3864 includes a one-pole lowpass filter that

limits the circuit bandwidth and improves noise perfor-

mance.

DC Cancellation Circuit

The DC cancellation circuit uses low-frequency feed-

back to remove the DC component of the input signal

(Figure 3). This feature centers the input signal within the

TIME

INPUT (AFTER DC CANCELLATION)

Figure 3. DC Cancellation Effect on Input

transimpedance amplifier’s linear range, thereby reduc-

ing pulse-width distortion (PWD) on large input signals.

The DC cancellation circuit is internally compensated

and therefore does not require external capacitors. This

circuit minimizes PWD for data sequences that exhibit a

50% duty cycle and mark density. A duty cycle or mark

density significantly different from 50% causes the

MAX3864 to generate PWD.

DC cancellation current is drawn from the input and

creates noise. For low-level signals with little or no DC

component, this is not a problem. Amplifier noise will

increase for signals with significant DC component (see

Typical Operating Characteristics).

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