參數(shù)資料
型號(hào)： OPA685N
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(yùn)算放大器商標(biāo)使用禁用
文件頁(yè)數(shù)： 22/28頁(yè)
文件大?。?/td> 283K
代理商： OPA685N
22
OPA685
The non-inverting inputs may be used to set the output DC
operating voltage independently of the signal path gain.
Measured single and 2-tone distortion results for the circuit
of Figure 12 are shown in Figure 13, where the outputs are
set to a +2.5V common-mode operating voltage to allow
direct coupling into a differential input, single +5V supply
ADC. This plot shows the SFDR for the worst harmonic
over frequency. The balanced differential structure of Figure
12 significantly improves SFDR at low frequencies while
holding the performance above 65dBc for a 1Vp-p output
through 60MHz.
85
80
75
70
65
60
55
5
15
25
35
45
55
65
75
Frequency (MHz)
S
V
CM
= +2.5V
V
O
= 1Vp-p
V
O
= 2Vp-p
FIGURE 13. Measured SFDR for Differential ADC Driver
(Figure 12).
DESIGN-IN TOOLS
DEMONSTRATION BOARDS
Two PC boards are available to assist in the initial evaluation
of circuit performance using the OPA685 in its two package
styles. Both of these are available free as an unpopulated PC
board delivered with descriptive documentation. The sum-
mary information for these boards is shown below.
BOARD
PART
NUMBER
LITERATURE
REQUEST
NUMBER
PRODUCT
PACKAGE
OPA685U
OPA681N
SO-8
SOT23-6
DEM-OPA68xU
DEM-OPA6xxN
MKT-351
MKT-348
Contact the Burr-Brown applications support line to request
any of these boards.
OPERATING SUGGESTIONS
SETTING RESISTOR VALUES TO OPTIMIZE BAND-
WIDTH
A current-feedback op amp like the OPA685 can hold an
almost constant bandwidth over signal gain settings with the
proper adjustment of the external resistor values. This is
shown in the Typical Performance Curves. The small-signal
bandwidth decreases only slightly with increasing gain.
These curves also show that the feedback resistor has been
changed for each gain setting. The resistor “values” on the
inverting side of the circuit for a current-feedback op amp
can be treated as frequency response compensation elements
while their “ratios” set the signal gain. Figure 14 shows the
analysis circuit for the OPA685 small-signal frequency re-
sponse.
FIGURE 14. Current-Feedback Transfer Function Analysis
Circuit.
R
F
V
O
R
G
R
I
Z
(S)
i
ERR
i
ERR
α
V
I
The key elements of this current feedback op amp model are:
α
Buffer gain from the non-inverting input to the invert-
ing input
R
I
Buffer output impedance
i
ERR
Feedback error current signal
Z(s)
Frequency dependent open-loop transimpedance
gain from i
ERR
to V
O
The buffer gain is typically very close to 1.00 and is
normally neglected from signal gain considerations. It will,
however, set the CMRR for a single op amp differential
amplifier configuration. For the buffer gain
α
<
1.0, the
CMRR = –20 log (1 –
α
).
相關(guān)PDF資料
PDF描述
OPA685U Ultra-Wideband, Current-Feedback OPERATIONAL AMPLIFIER With Disable TM
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
OPA685N/250 制造商:未知廠(chǎng)家 制造商全稱(chēng):未知廠(chǎng)家 功能描述:Current-Feedback Operational Amplifier
OPA685N/3K 制造商:未知廠(chǎng)家 制造商全稱(chēng):未知廠(chǎng)家 功能描述:Current-Feedback Operational Amplifier
OPA685U 功能描述:高速運(yùn)算放大器 Ultra-Wideband RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)償電壓:0.5 mV 轉(zhuǎn)換速度:55 V/us 工作電源電壓:36 V 電源電流:7.5 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube
OPA685U/2K5 制造商:未知廠(chǎng)家 制造商全稱(chēng):未知廠(chǎng)家 功能描述:Current-Feedback Operational Amplifier
OPA686 制造商:BB 制造商全稱(chēng):BB 功能描述:Wideband, Low Noise, Voltage Feedback OPERATIONAL AMPLIFIER
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