Preliminary Data Sheet
January 1998
LG1628AXA SONET/SDH 2.488 Gbits/s
Transimpedance Amplifier
7
Lucent Technologies Inc.
Test Circuit with Overload Control
5-5335(F)r.1
1.
Operational amplifiers OP1 and OP2 should have the following characteristics (suggested op amps are the LMC6082IM or OP291GS, both
are available as dual op amps in an 8-pin SOIC package):
a.Single 5 V supply operation.
b.Maximum input offset voltage of 1 mV.
c.Low-level output includes negative rail.
An on-chip 75 k
resistor to the negative supply is provided for biasing the voltage reference. Approximately 100
drawn. (Suggested bandgap reference is the LM4040BIM–2.5, available in an SOT-23 package.)
Node IN+ is nominally at –3.3 Vdc. APD supply voltage +V
det
should be adjusted appropriately.
R
IN
L
IN
may be necessary to achieve stability depending on the physical arrangement of the APD and its associated electrical parasitics
(series inductance and other resonances). The amplifier will be stable with a 0.5 pF detector capacitance in series with a 0.5 nH inductor,
but packaged detectors usually do not behave so ideally at frequencies above a few gigahertz. A parallel RL network consisting of a 200
resistor and a 6 nH inductor is provided on HIC and may be optionally used with a slight noise penalty. Good isolation from output to input
is also essential for amplifier stability.
A low-pass filter is provided on the LG1628AXA HIC to reduce higher-frequency noise contributions (Butterworth N = 2, Zo
= 50 and fc
=
4.25 GHz, L
OUT
= 2.65 nH, C
OUT
= 0.5 pF).
d.High-level output to within 2 V of the positive rail.
e.Gain bandwidth product
f. Large signal voltage gain
≥
1.8 MHz.
≥
100 V/mV.
2.
μ
A of current will be
3.
4.
5.
Figure 4. Optical Receiver with Overload Control
OP1
1
–
+
OP2
1
–
+
3
4
5
6
7
8
9
10
11
12
0.047
μ
F
0.047
μ
F
0.047
μ
F
0.047
μ
F
300 pF
+
5.2 V
+V
DET
0.1
μ
F 10
100 pF
Vss
G
1
V
S
Z
EFF
50
LIMITING
BUFFER
OUT+
R
F
OUT–
R
F
IN–
IN+
B
O
O
O
O
O
O
O
O
O
V
S
G
2
OVERLOAD CONTROL
1
14
15
18
19
24
0.02
μ
F
300 pF
0.047
μ
F
0.047
μ
F
50
50
APD
27 k
V
SS1
BG
17
2.5 V
BANDGAP
2
~100
μ
A
10
100 pF
0.033
μ
F
50
1 k
APD+
(SEE NOTE 3 FOR BIAS CONDITIONS)
R
IN
L
IN
L
OUT
L
OUT
C
OUT
(LPF, SEE NOTE 5)
100 V CAPS
(SEE NOTE 4)