303 South Technology Court

Phone: (800) SMI-MMIC

http://www.sirenza.com

Broomfield, CO 80021

4

EDS-102714 Rev. D

Preliminary Data Sheet

SFT-0100 Transimpedance Amplifier

DCDR

IMON

GND

OUTP

GND

OUTN

GND

GND

GND

IN

GND

GND

VCC

CEXT

Zo = 50

Ω

Zo = 50

Ω

Zo = 50

Ω

IN

OUTN

OUTP

100pF

1000pF 0.1uF

100pF

1000pF

0.1uF

Imon

Vcc (5V)

Vcc (5V)

100pF

1000pF 0.1uF

100pF

1000pF

0.1uF

R

DCDR

(1K-50K

Ω, optional)

Application Circuit

Description of External Connections and How They Operate

Imon: When tied to the supply voltage through an amme-

ter, the current through the ammeter “Imon” reflects the

average photo diode current. The Imon current will be

approximately the value of the average photo diode cur-

rent and will be directly proportional to this quantity. Imon

can be used for loss of signal detection or photodiode/fiber

alignment in manufacturing. A third function this monitor

can provide is the manual adjustment of the DCDR thresh-

old. With no input photocurrent applied to the TIA, the

Imon will give a finite quiescent current (uA). The finite cur-

rent indicates that the automatic circuit has already started

to turn on. By employing a shunt resistor (1K-50K) on the

rent can be reduced to a few uA) setting the automatic cir-

cuit for maximum sensitivity and dynamic range.

DCDR (Duty Cycle Distortion Reduction): This patented

feature compensates for the duty cycle distortion as a

result of high input current seen by the amplifier. As the

optical input power and induced photo current is

increased, an automatic circuit is invoked to prevent dis-

torted operation in the transistors of the TIA. The threshold

input current where the circuit turns on can be adjusted by

employing a shunt resistor to ground at the DCDR pin. The

value of the shunt resistor can be set between 1K and

50K. The lower the value, the higher the input current

threshold in which the circuit turns on. In order to optimize

for maximum sensitivity and dynamic range, the Imon cur-

rent can be monitored while tuning this shunt resistor.

Optimum sensitivity and dynamic range can be obtained

by tuning the resistor value until only a few uA of Imon cur-

rent is observed when there is no optical input power

applied.

grate and produce the automatic circuit control voltage.

operation for the amplifier. For 30KHz operation and

below, a 0.1uF capacitor is required. Wirebond length is

critical and should be minimized.

length is critical and should be minimized.

Ground Wirebonds: The SFT-0100 has backside vias

and backside metal. The bottom of the die must be electri-

cally connected to ground using eutectic or conductive

epoxy die attach methods. It is not recommended to attach

any wirebonds to the top GND pads.