REV. A
–6–
AD8015
100
50
1
10 100
1000
FREQUENCY – MHz
0
5V, +25°C
PIN 7
PIN 6
IMPEDANCE – Ω
Figure 12. Output Impedance vs. Frequency
100
–100
200
0
10
TIME – ns
VOLTAGE – mV
Figure 13. Small Signal Pulse Response
2
0
–12
10.0E+6 100.0E+6 1.0E+9
–2
–4
–6
–8
–10
0pF
1pF
3pF
5pF
8pF
FREQUENCY – Hz
GAIN – dB
Figure 14. Differential Gain vs. Input Capacitance
APPLICATION
155 Mbps Fiber Optic Receiver
The AD8015 and AD807 can be used together for a complete
155 Mbps Fiber Optic Receiver (Transimpedance Amplifier,
Post Amplifier with Signal Detect Output, and Clock Recovery
and Data Retiming) as shown in Figure 16.
The PIN diode front end is connected to a single mode, 1300 nm
laser source. The PIN diode has 3.3 V reverse bias, 0.8 A/W
responsivity, 0.7 pF capacitance, and 2.5 GHz bandwidth.
The AD8015 outputs (P
OUT
and N
OUT
) drive a differential, con-
stant impedance (50 Ω) low-pass π filter with a 3 dB cutoff of
100 MHz. The outputs of the low-pass filter are ac coupled to
the AD807 inputs (PIN and NIN). The AD807 PLL damping
factor is set at 10 using a 0.22 µF capacitor.
The entire circuit was enclosed in a shielded box. Table I sum-
marizes results of tests performed using a 2
23
–1 PRN sequence,
and varying the average power at the PIN diode.
The circuit acquires and maintains lock with an average input
power as low as –39.25 dBm.
80
0
20
10
200.000E+6
40
30
50
60
70
80
0
20
10
40
30
50
60
70
90
100
205.000E+6
215.000E+6
220.000E+6
225.000E+6
230.000E+6
235.000E+6
240.000E+6
245.000E+6
250.000E+6
255.000E+6
260.000E+6
265.000E+6
270.000E+6
275.000E+6
280.000E+6
285.000E+6
290.000E+6
295.000E+6
300.000E+6
210.000E+6
30 DEVICES, 2 LOTS:
(+OUT, –OUT) × (25°C, –40°C, 85°C) × (5V, 4.5V, 11.0V)
FREQUENCY – Hz
POPULATION – Parts
CUMULATIVE – %
Figure 15. Bandwidth Distribution Matrix
