HFBR-2464K Просмотр технического описания (PDF) - HP => Agilent Technologies

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HFBR-2464K

Low Cost, Miniature Fiber Optic Components with ST®, SMA, SC and FC Ports

HP => Agilent Technologies 

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 appro-

priate circuit techniques. The

LED drive circuit shown in

Figure 11 uses frequency com-

pensation 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 dis-

tortion of less than 1 ns. This

circuit is recommended for appli-

cations 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 Hewlett-

Packard Application Bulletin 78

and Application Note 1038.

Ry = –(V–C––C–-–V–F–)––+––3–.–9–7–(–V–C–C––-–V–F––-–1–.–6–V––)

IF ON (A)

( ) RX1 = –1 ––R–y–

2 3.97

REQ2(Ω) = RX1 - 1

RX2 = RX3 = RX4 = 3(REQ2)

C(pF) = 2––0–0–0–(–p–s–)

RX1(Ω)

Example for IF ON = 100 mA: VF can be

obtained from Figure 9 (= 1.84 V).

Ry = –(5––-–1–.–8–4–)––+––3–.–9–7–(–5––-–1–.–8–4––- –1–.6––)

0.100

Ry = –3–.1–6––+––6–.–1–9– = 93.5 Ω

0.100

( ) RX1 = 1– –9–3–.5– = 11.8 Ω

2 3.97

REQ2 = 11.8 - 1 = 10.8 Ω

RX2 = RX3 = RX4 = 3(10.8) = 32.4 Ω

C = 2–0––0–0–p––s = 169 pF

11.8 Ω

63

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