AD847JRZ Datasheet, PDF (10/12 Pages) List of Unclassifed Manufacturers – MICROCIRCUIT, LINEAR, HIGH SPEED, LOW POWER, OPERATIONAL AMPLIFIER, MONOLITHIC SILICON

AD847
VIDEO LINE DRIVER
The AD847 functions very well as a low cost, high speed line
driver for either terminated or unterminated cables. Figure 23
shows the AD847 driving a doubly terminated cable in a fol-
lower configuration.
The termination resistor, R_T, (when equal to the cable’s charac-
teristic impedance) minimizes reflections from the far end of the
cable. While operating from ± 5 V supplies, the AD847 main-
tains a typical slew rate of 200 V/µs, which means it can drive a
± 1 V, 30 MHz signal into a terminated cable.
+V_S
75Ω
COAX
V_IN
R _IN
100Ω
75Ω
AD847
–V_S
0.1 µF
75Ω
COAX
R _BT
75Ω
0.1 µF
500Ω
V_OUT
R_T
75Ω
C_C
SEE TABLE I
500Ω
Figure 23. Video Line Driver
Table I. Video Line Driver Performance Chart
V_IN*
0 dB or ± 500 mV Step
0 dB or ± 500 mV Step
0 dB or ± 500 mV Step
0 dB or ± 500 mV Step
0 dB or ± 500 mV Step
0 dB or ± 500 mV Step
V_SUPPLY
± 15
± 15
± 15
±5
±5
±5
Over-
C_C –3 dB B_W shoot
20 pF 23 MHz 4%
15 pF 21 MHz 0%
0 pF 13 MHz 0%
20 pF 18 MHz 2%
15 pF 16 MHz 0%
0 pF 11 MHz 0%
*–3 dB bandwidth numbers are for the 0 dBm signal input. Overshoot numbers
are the percent overshoot of the 1 volt step input.
A back-termination resistor (R_BT, also equal to the characteristic
impedance of the cable) may be placed between the AD847 out-
put and the cable input, in order to damp any reflected signals
caused by a mismatch between R_T and the cable’s characteristic
impedance. This will result in a flatter frequency response, al-
though this requires that the op amp supply ± 2 V to the output
in order to achieve a ± 1 V swing at resistor R_T.
Figure 24 shows the AD847 driving 100 pF and 1000 pF loads.
Figure 24. AD847 Driving Capacitive Loads
FLASH ADC INPUT BUFFER
The 35 MHz unity gain bandwidth of the AD847 makes it an
excellent choice for buffering the input of high speed flash A/D
converters, such as the AD9048.
Figure 25 shows the AD847 as a unity inverter for the input to
the AD9048.
ANALOG
INPUT
(0V TO +2V)
TTL
CONVERT
SIGNAL
0.1
AD589
10kΩ
–5.2V
2k
0.1
1k
1.5kΩ
1.5kΩ
50Ω
AD847
100
AD741
1k
27
2N3906
5
0.1µF
43Ω
R_B
V_IN
R_T
D1
(MSB)
0.1µF
AD9048
CONVERT
D8
(LSB)
V_EE V_CC
0.1µF
–5.2V +5.0V
Figure 25. Flash ADC Input Buffer
–10–
REV. F