NE5210 Philips, NE5210 Datasheet - Page 12

• Manufacturer Part Number: NE5210
• Description: Transimpedance amplifier 280MHz
• Manufacturer: Philips

Philips Semiconductors
The operating point of Q1, Figure 2, has been optimized for the
lowest current noise without introducing a second dominant pole in
the pass-band. All poles associated with subsequent stages have
been kept at sufficiently high enough frequencies to yield an overall
single pole response. Although wider bandwidths have been
achieved by using a cascode input stage configuration, the present
solution has the advantage of a very uniform, highly desensitized
frequency response because the Miller effect dominates over the
external photodiode and stray capacitances. For example, assuming
a source capacitance of 1pF, input stage voltage gain of 70, R
60 then the total input capacitance, C
lead to only a 12% bandwidth reduction.
NOISE
Most of the currently installed fiber-optic systems use non-coherent
transmission and detect incident optical power. Therefore, receiver
noise performance becomes very important. The input stage
achieves a low input referred noise current (spectral density) of
3.5pA/ Hz. The transresistance configuration assures that the
external high value bias resistors often required for photodiode
biasing will not contribute to the total noise system noise. The
equivalent input
quiescent current of Q
bandwidth; however, it is not dependent upon the internal
Miller-capacitance. The measured wideband noise was 66nA
a 200MHz bandwidth.
DYNAMIC RANGE CALCULATIONS
The electrical dynamic range can be defined as the ratio of
maximum input current to the peak noise current:
Electrical dynamic range, D
I
external source capacitance of C
D
In order to calculate the optical dynamic range the incident optical
power must be considered.
1995 Apr 26
INMAX
E
Transimpedance amplifier (280MHz)
= 240 A and a wideband noise of I
20log
I
IN
V
IN
(Peak noise current) (RMS)
20 log
Figure 3. Shunt-Series Input Stage
INPUT
RMS
(Max. input current) (PK)
noise current is strongly determined by the
( 2 66 10
(240 10
1
, the feedback resistor R
I
F
I
B
E
, in a 200MHz bandwidth assuming
R1
S
6
9
)
Q1
)
= 1pF.
R
F
I
IN
C1
68dB
= (1+7.5) pF which will
EQ
=66nA
Q2
2
R2
F
, and the
RMS
Q3
R3
V
R4
EQ3
for an
V
CC
SD00329
RMS
IN
=
in
12
For a given wavelength ; (meters)
Energy of one Photon = hc watt sec (Joule)
Where h=Planck’s Constant = 6.6
c = speed of light = 3
c /
No. of incident photons/sec= where P=optical incident power
No. of incident photons/sec =
where P = optical incident power
No. of generated electrons/sec =
where
where e = electron charge = 1.6
Responsivity R =
Assuming a data rate of 400 Mbaud (Bandwidth, B=200MHz), the
noise parameter Z may be calculated as:
where Z is the ratio of
single hole-electron pair. Assuming 100% photodetector quantum
efficiency, half mark/half space digital transmission, 850nm
lightwave and using Gaussian approximation, the minimum required
optical power to achieve 10
where h is Planck’s Constant, c is the speed of light,
wavelength. The minimum input current to the NE5210, at this input
power is:
Choosing the maximum peak overload current of I
maximum mean optical power is:
Thus the optical dynamic range, D
D
I
Z
P
O
avMAX
= P
P
= optical frequency (Hz)
I
I
P
no. of generated electron hole paris
avMIN
avMIN
I
qB
avMAX
EQ
= quantum efficiency
R
= 792nA
no. of incident photons
hcI
1139nW
- P
hs e Amps (Coulombs sec.)
P
(1.6 10
12 hc B Z
200 10
qP
1139 10
avMAX
avMIN
q
avMIN
hs Amp/watt
e
66 10
RMS
= -4.6 -(-29.4) = 24.8dB.
2.3 10
10
hc
6
19
2.3 10
1.6 10
8
2063
9
noise output to the peak response to a
)(200 10
-9
m/sec
12 2.3 10
29.4dBm
BER is:
1.6 10
hs
P
9
19
10
O
19
19
10
is:
-19
240 10
6
hs
P
)
-34
19
Coulombs
1
Joule sec.
19
2063
6
Product specification
avMAX
NE5210
is the
=240 A, the