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參數(shù)資料
| 型號： | OPA4684IPWT |
| 英文描述： | Quad, Low-Power, Current-Feedback OPERATIONAL AMPLIFIER |
| 中文描述： | 四，低功耗，電流反饋運算放大器 |
| 文件頁數(shù)： | 17/26頁 |
| 文件大小： | 455K |
| 代理商： | OPA4684IPWT |
OPA4684
SBOS240B
17
www.ti.com
DUAL-CHANNEL, DIFFERENTIAL ADC DRIVER
Where a low-power, single-supply, interface to a differential
input +5V ADC is required, the circuit of Figure 12 can
provide a high dynamic range, medium gain interface for
dual high-performance ADCs. The circuit of Figure 12 uses
two amplifiers in the differential inverting configuration. The
common-mode voltage is set on the noninverting inputs to
the supply midscale. In this example, the input signal is
coupled in through a 1:2 transformer. This provides both
signal gain, single to differential conversion, and a reduction
in noise figure. To show a 50
input impedance at the input
to the transformer, two 200
resistors are required on the
transformer secondary. These two resistors are also the
amplifier gain elements. Since the same DC voltage appears
on both inverting nodes in the circuit of Figure 12, no DC
current will flow through the transformer, giving a DC gain of
1 to the output for this common-mode voltage, V
CM
.
The circuit of Figure 12 is particularly suitable for a moderate
resolution dual ADC used as I/Q samplers. The optional
500
resistors to ground on each amplifier output can be
added to improve the 2nd- and 3rd-harmonic distortion by
> 15dB if higher dynamic range is required. Figure 13 shows
the harmonic distortion for the circuit of Figure 12 with and
without these pull-down resistors. The 5mA added output
stage current significantly improves linearity if that is re-
quired. The measured 2nd-harmonic distortion is consis-
tently lower than the 3rd-harmonics for this balanced differ-
ential design. It is particularly helpful for this low-power
design if there are no grounds in the signal path after the low-
level signal at the transformer input. The two pull-down
resistors do show a signal path ground and should be
connected at the same physical point to ground to eliminate
imbalanced ground return currents from degrading 2nd-
harmonic distortion.
DESIGN-IN TOOLS
DEMONSTRATION BOARDS
Two PC boards are available to assist in the initial evaluation
of circuit performance using the OPA4684 in its two package
styles. Both of these are available, free, as an unpopulated
PC board delivered with descriptive documentation. The
summary information for these boards is shown in Table I
below.
+5V
1/4
OPA4684
1/4
OPA4684
800
800
R
S
R
S
14.7dB
Noise Figure
Gain = 8V/V
18.1dB
200
200
10k
10k
0.1
μ
F
V
CM
C
L
500
500
V
CM
Dual ADC
1 of 2
Channels
1:2
50
Source
FIGURE 12. Single-Supply Differential ADC Driver (1 of 2 Channels).
BOARD
PART
NUMBER
LITERATURE
REQUEST
NUMBER
PRODUCT
PACKAGE
OPA4684ID
OPA4684IDBW
SO-14
TSSOP-14
DEM-OPA468xD
DEM-OPA46xxDPW
SBOU016
—
TABLE I. Evaluation Module Ordering Information.
FIGURE 13. Harmonic Distortion vs Frequency.
Frequency (MHz)
H
1
10
20
–
50
–
60
–
70
–
80
–
90
2nd-Harmonic
No Pull-Down
3rd-Harmonic
3rd-Harmonic
2nd-Harmonic
2Vp-p Output
5mA/Ch Pull-Down
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA4684IPWTG4 | 功能描述:高速運算放大器 Quad Low-Power Current Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補償電壓: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 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| OPA4684M | 制造商:TI 制造商全稱:Texas Instruments 功能描述:QUAD LOW-POWER CURRENT-FEEDBACK OPERATIONAL AMPLIFIER |
| OPA4684MJD | 制造商:Texas Instruments 功能描述:QUAD, LOW-POWER, CURRENT-FEEDBACK OP AMP - Rail/Tube |
| OPA4703 | 制造商:BB 制造商全稱:BB 功能描述:CMOS, Rail-to-Rail, I/O OPERATIONAL AMPLIFIERS |
| OPA4703EA | 制造商:TI 制造商全稱:Texas Instruments 功能描述:CMOS, Rail-to-Rail, I/O OPERATIONAL AMPLIFIERS |
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