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| 型號： | ADA4937-2YCPZ-R7 |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 11/29頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC ADC DRIVER DIFF DUAL 24LFCSP |
| 標(biāo)準(zhǔn)包裝： | 1 |
| 類型： | ADC 驅(qū)動器 |
| 應(yīng)用： | 數(shù)據(jù)采集 |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 24-VFQFN 裸露焊盤，CSP |
| 供應(yīng)商設(shè)備封裝： | 24-LFCSP-VQ（4x4） |
| 包裝： | 標(biāo)準(zhǔn)包裝 |
| 產(chǎn)品目錄頁面： | 765 (CN2011-ZH PDF) |
| 其它名稱： | ADA4937-2YCPZ-R7DKR |
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ADA4937-1/ADA4937-2
Data Sheet
Rev. D | Page 18 of 28
THEORY OF OPERATION
The ADA4937-x differs from conventional op amps in that it
has two outputs whose voltages move in opposite directions.
Like an op amp, it relies on open-loop gain and negative feed-
back to force these outputs to the desired voltages. The ADA4937-
x behaves much like a standard voltage feedback op amp, which
makes it easier to perform single-ended-to-differential conversions,
common-mode level shifting, and amplifications of differential
signals. Also like an op amp, the ADA4937-x has high input
impedance and low output impedance.
Two feedback loops control the differential and common-mode
output voltages. The differential feedback loop, set with external
resistors, controls only the differential output voltage. The
common-mode feedback loop controls only the common-mode
output voltage. This architecture makes it easy to set the output
common-mode level to any arbitrary value. It is forced, by
internal common-mode feedback, to be equal to the voltage
applied to the VOCM input without affecting the differential
output voltage.
The ADA4937-x architecture results in outputs that are highly
balanced over a wide frequency range without requiring tightly
matched external components. The common-mode feedback
loop forces the signal component of the output common-mode
voltage to zero. This results in nearly perfectly balanced differential
outputs that are identical in amplitude and are exactly 180° apart
in phase.
ANALYZING AN APPLICATION CIRCUIT
The ADA4937-x uses open-loop gain and negative feedback to
force its differential and common-mode output voltages in such
a way as to minimize the differential and common-mode error
voltages. The differential error voltage is defined as the voltage
between the differential inputs labeled +IN and IN (see
Figure 52). For most purposes, this voltage can be assumed
to be zero. Similarly, the difference between the actual output
common-mode voltage and the voltage applied to VOCM can
also be assumed to be zero. Starting from these two assumptions,
any application circuit can be analyzed.
SETTING THE CLOSED-LOOP GAIN
The differential-mode gain of the circuit in Figure 52 can be
determined by
G
F
dm
IN
dm
OUT
R
V
=
,
This assumes that the input resistors (RG) and feedback resistors
(RF) on each side are equal.
ESTIMATING THE OUTPUT NOISE VOLTAGE
The differential output noise of the ADA4937-x can be esti-
mated using the noise model in Figure 53. The input-referred
noise voltage density, vnIN, is modeled as a differential input, and
the noise currents, inIN and inIN+, appear between each input and
ground. The noise currents are assumed to be equal and produce
a voltage across the parallel combination of the gain and feedback
resistances. vn,cm is the noise voltage density at the VOCM pin. Each
Table 9 summarizes the input noise sources, the multiplication
factors, and the output-referred noise density terms.
ADA4937
+
RF2
VnOD
VnCM
VOCM
VnIN
RF1
RG2
RG1
VnRF1
VnRF2
VnRG1
VnRG2
inIN+
inIN–
06591-
050
Figure 53. ADA4937-x Noise Model
Table 9. Output Noise Voltage Density Calculations
Input Noise Contribution
Input Noise Term
Input Noise
Voltage Density
Output
Multiplication Factor
Output Noise
Voltage Density Term
Differential Input
vnIN
GN
vnO1 = GN(vnIN)
Inverting Input
inIN
inIN × (RG2||RF2)
GN
vnO2 = GN[inIN × (RG2||RF2)]
Noninverting Input
inIN+
inIN+ × (RG1||RF1)
GN
vnO3 = GN[inIN+ × (RG1||RF1)]
VOCM Input
vn, cm
GN(β1 β2)
vnO4 = GN(β1 β2)(vn, cm)
Gain Resistor RG1
vnRG1
(4kTRG1)1/2
GN(1 β1)
vnO5 = GN(1 β1)(4kTRG1)1/2
Gain Resistor RG2
vnRG2
(4kTRG2)1/2
GN(1 β2)
vnO6 = GN(1 β2)(4kTRG2)1/2
Feedback Resistor RF1
vnRF1
(4kTRF1)1/2
1
vnO7 = (4kTRF1)1/2
Feedback Resistor RF2
vnRF2
(4kTRF2)1/2
1
vnO8 = (4kTRF2)1/2
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| ADA4937-2YCPZ-RL | 功能描述:IC ADC DRIVER DUAL DIFF 24LFCSP RoHS:是 類別:集成電路 (IC) >> 線性 - 放大器 - 專用 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:60 系列:- 類型:可變增益放大器 應(yīng)用:CATV 安裝類型:表面貼裝 封裝/外殼:20-WQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:20-TQFN-EP（5x5） 包裝:托盤 |
| ADA4938-1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Ultra-Low Distortion Differential ADC Driver |
| ADA4938-1_06 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Ultra-Low Distortion Differential ADC Driver |
| ADA4938-1_07 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Ultra-Low Distortion Differential ADC Driver |
| ADA4938-1ACPZ-R2 | 制造商:Analog Devices 功能描述:SP Amp DIFF AMP Single ±5.5V/11V 16-Pin LFCSP EP T/R 制造商:Analog Devices 功能描述:SP AMP DIFF AMP SGL 5.5V/11V 16LFCSP EP - Tape and Reel 制造商:Analog Devices 功能描述:SP Amp DIFF AMP Single }5.5V/11V 16-Pin LFCSP EP Tape & Reel 制造商:Analog Devices 功能描述:IC AMP DIFFADCDR16BIT16LFCSP |
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