Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

4

___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600

© 1994 Maxim Integrated Products

Printed USA

is a registered trademark of Maxim Integrated Products.

1GHz Transimpedance Preamplifier

with 25dB Dynamic Range

_______________________Wire Bonding

For high current density and reliable operation, the

MAX3260 uses gold metallization. Connections to the

die should be made with gold wire only, using ball

bonding techniques. Wegde bonding is not recom-

mended. Die pad size is 4 mils.

__________________Design Procedure

The MAX3260 is a high-speed, high-gain component.

Its performance is strongly affected by module design

and layout. Improper design techniques can cause

oscillations or ringing.

In fiber-optic receiver applications, it is highly recom-

mended that the transimpedance preamplifier be

placed close to the photodetector, in the same pack-

age or header if possible. This reduces parasitic induc-

tance and improves static-discharge protection during

manufacturing. An alternative layout is to assemble the

preamplifier on a hybrid circuit board. In either case,

the designer should ensure that power-supply runs to

ground connections to the MAX3260 short and mini-

mize inductance. Multiple vias may be required when

connecting to the ground plane on a circuit board, to

reduce the ground inductance.

The MAX3260 will typically be connected to a limiting

or post amplifier by means of a controlled-impedance

transmission line. If a transmission line is used, it is

important to end-terminate the line with the characteris-

tic impedance to prevent reflections into the output of

the MAX3260.

__________Applications Information

The MAX3260 consumes approximately 23mA of cur-

rent with no output load. Typically, the majority of power

used by the preamplifier is consumed in the output ter-

mination. The termination is needed at the end of the

transmission line connecting MAX3260 to a limiting

amplifer. The average output level is typically 1.6V, and

is maintained at that level by the DC-restore function. A

50

Ω termination to ground will consume 32mA of stand-

ing current. Power consumption can be reduced by ter-

minating to higher resistance. A 75

Ω transmission line

and termination would consume only 22mA. Power con-

sumption can be reduced dramatically by excluding

the transmission line and termination, which requires

very short distances between the MAX3260 and the fol-

lowing circuit.

DC RESTORE

CIRCUIT

FILTER

1.6V

2.5k

4k

1k

COMPARATOR

MAX3260

Figure 1. Functional Diagram