參數(shù)資料
型號： OPA685U
元件分類： 運動控制電子
英文描述： Ultra-Wideband, Current-Feedback OPERATIONAL AMPLIFIER With Disable TM
中文描述： 超寬帶，電流反饋運算放大器商標使用禁用
文件頁數(shù)： 20/28頁
文件大?。?/td> 283K
代理商： OPA685U
20
OPA685
An alternative circuit that will take advantage of the higher
inverting slew rate of the OPA685 (4200V/
μ
s), takes the
complementary current output from the RAMDAC and
converts it to positive video to give a very high full power
bandwidth RGB line driver. This will give sharper pixel
edges than the circuit of Figure 8. Most high-speed DACs
are current-steering designs where there is both an output
current signal that is used for the video, and a complemen-
tary output that is typically discarded into a matching resis-
tor. The complementary current output can be used as an
auxiliary output if it is inverted as shown in Figure 9.
In the circuit of Figure 9, the complementary current output
is terminated by an equivalent 75
impedance (the parallel
combination of R
T
and R
G
) that also provides a current
division to reduce the signal current through the feedback
resistor, R
F
. This allows R
F
to be increased to a value which
will hold a flat frequency response. Since the complemen-
tary current output is essentially an inverted video signal,
this circuit sets up a white video level at the output of the
OPA685 for zero DAC output current (using the 0.77V DC
bias on the non-inverting input), then inverts the comple-
mentary output current to produce a signal that ranges from
this 1.4V at zero output current down to 0V at maximum
output current level (assuming a 20mA maximum output
current). This will give a very wideband (> 400MHz) video
signal capability.
ARBITRARY WAVEFORM DRIVER
The OPA685 may be used as the output stage for moderate
output power Arbitrary Waveform Driver applications. Driv-
ing out through a series 50
matching resistor into a 50
matched load will allow up to a 3.6Vp-p swing at the
matched load (15dBm) when operating the OPA685 on a
±
5V power supply. This level of power is available for gains
of either
±
8 with a flat response through 100MHz. When
interfacing directly from a complementary current output
DAC, consider the circuit of Figure 9, modified for the peak
output currents of the particular DAC being considered.
Where purely AC-coupled output signals are required from
a complementary current output DAC, consider a push-pull
output stage using the circuit of Figure 10. The resistor
values here have been calculated for a 20mA peak output
current DAC which produces up to a 5Vp-p swing at the
matched load (18dBm). This approach will give higher
power at the load with much lower 2nd harmonic distortion.
FIGURE 9. High Resolution RGB Driver Using DAC Complementary Output Current.
FIGURE 10. High Power, Wideband AC-Coupled ARB Driver.
OPA685
+5V
–5V
+5V
–5V
464
66.5
0.01
μ
F
200
20
50
OPA685
464
66.5
0.01
μ
F
200
50
DAC
20mA Peak Output
Differential
Filter
I
O
I
O
50
Source
1.4:1
±
3.5V
±
3.5V
Power supply decoupling not shown.
20
DIS
DIS
OPA685
75
R
F
500
R
G
536
R
T
86.6
+5V
Power supply decoupling not shown.
–5V
RAMDAC
768
4.22
0.77V
I
O
20
0.1
μ
F
DIS
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
OPA685U/2K5 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Current-Feedback Operational Amplifier
OPA686 制造商:BB 制造商全稱:BB 功能描述:Wideband, Low Noise, Voltage Feedback OPERATIONAL AMPLIFIER
OPA686N 制造商:BB 制造商全稱:BB 功能描述:Wideband, Low Noise, Voltage Feedback OPERATIONAL AMPLIFIER
OPA686N/250 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Texas Instruments 功能描述:
OPA686N/3K 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Texas Instruments 功能描述:
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