HFBR-24E5TM View Datasheet(PDF) - HP => Agilent Technologies
Part Name
Description
MFG CO.
HFBR-24E5TM
HP => Agilent Technologies
'HFBR-24E5TM' PDF : 25 Pages View PDF
Recommended Drive Circuits
The circuit used to supply
current to the LED transmitter
can significantly influence the
optical switching characteristics
of the LED. The optical rise/fall
times and propagation delays
can be improved by using the
appropriate circuit techniques.
The LED drive circuit shown in
Figure 11 uses frequency
compensation to reduce the
typical rise/fall times of the LED
and a small pre-bias voltage to
minimize propagation delay
differences that cause pulse-
width distortion. The circuit will
typically produce rise/fall times
of 3 ns, and a total jitter
including pulse-width distortion
of less than 1 ns. This circuit is
recommended for applications
requiring low edge jitter or high-
speed data transmission at
signal rates of up to 155 MBd.
Component values for this
circuit can be calculated for
different LED drive currents
using the equations shown
below. For additional details
about LED drive circuits, the
reader is encouraged to read
Agilent Application Bulletin 78
and Application Note 1038.
RY (VCC − VF) + 3.97(VCC − VF − 1.6V)
IF ON (A)
RX1 = 1 RY
2 3.97
REQ2 (Ω) = RX1 − 1
RX2 = RX3 = RX4 = 3(REQ2)
C(pF) = 2000 ps
RX1(Ω)
Example for IF ON = 100mA :
VF can be obtained from Figure 9 (= 1.84 V).
RY = (5 −1.84) + 3.97(5 − 1.84 − 1.6)
0.100
RY = 3.16 + 6.19 = 93.5 Ω
0.100
RX1 = 1 93.5 = 11.8 Ω
2 3.97
REQ2 = 11.8 - 1 = 10.8 Ω
RX2 = RX3 = RX4 = 3 (10.8) = 32.4 Ω
C = 2000 ps = 169 pF
11.8 Ω
18
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