OPA2830_08 Datasheet, PDF (25/41 Pages) Burr-Brown (TI) – Dual, Low-Power, Single-Supply, Wideband OPERATIONAL AMPLIFIER

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This circuit gives a voltage gain of 2 at the output pin
with a high-pass pole at 8Hz. Given the 150Ω load, a
simple blocking capacitor approach would require a
133µF value. The two much lower valued capacitors
give this same low-pass pole using this simple SAG
correction circuit of Figure 76.
The input is shifted slightly positive in Figure 76
using the voltage divider from the positive supply.
This gives about a 200mV input DC offset that will
show up at the output pin as a 400mV DC offset
when the DAC output is at zero current during the
sync tip portion of the video signal. This acts to hold
the output in its linear operating region. This will pass
on any power-supply noise to the output with a gain
of approximately –20dB, so good supply decoupling
is recommended on the power-supply pin. Figure 75
shows the frequency response for the circuit of
Figure 76. This plot shows the 8Hz low-frequency
high-pass pole and a high-end cutoff at
approximately 100MHz.
+5V
Video DAC
1.87kΩ
78.7Ω
1/2
OPA2830
325Ω
650Ω
OPA2830
SBOS309C – AUGUST 2004 – REVISED MARCH 2006
3
0
−3
−6
−9
−12
−15
−18
−21
1
10 10² 10³ 10⁴ 10⁵ 10⁶ 10⁷ 10⁸ 10⁹
Frequency (Hz)
Figure 75. Video Line Driver Response to
Matched Load
47µ F
845Ω
528Ω
75Ω
22µF
V_O
75Ω Load
Figure 76. Video Line Driver with SAG Correction
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