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參數(shù)資料
| 型號(hào)： | LT5514EFE |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類(lèi)： | 模擬信號(hào)調(diào)理 |
| 英文描述： | Ultralow Distortion IF Amplifier/ADC Driver with Digitally Controlled Gain |
| 中文描述： | SPECIALTY ANALOG CIRCUIT, PDSO20 |
| 封裝： | 4.40 MM, PLASTIC, TSSOP-20 |
| 文件頁(yè)數(shù)： | 15/20頁(yè) |
| 文件大小： | 275K |
| 代理商： | LT5514EFE |
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15
LT5514
5514f
gain output amplifier. The overall gain of the LT5514 is
digitally controlled by means of four gain control pins with
internal pull-down. Minimum gain is programmed when
the gain control pins are set low or left floating. In
shutdown mode, these PGA inputs draw <10
μ
A leakage
current, regardless of the applied voltage.
The 6dB and 12dB attenuation steps (PGA2 and PGA3) are
implemented by switching the amplifier inputs to an input
attenuator tap. The 3dB attenuation step (PGA1) changes
the amplifier transconductance. The output IP3 is approxi-
mately independent of the PGA1, PGA2 and PGA3 gain
settings. However, the 1.5dB attenuation step utilizes a
current steering technique that disables the internal linear-
ity compensation circuit, and the OIP3 can be reduced by
as much as 6dB when PGA0 is low. Therefore, to achieve
the LT5514’s highest linearity performance, the PGA0 pin
should be set high.
The LT5514 noise figure is 7.3dB in the maximum gain state.
For the –3dB attenuation setting, the NF is 7.6dB. The noise
figure increases in direct proportion to the amount of pro-
grammed gain reduction for the 1.5dB, 6dB and 12dB steps.
The output noise floor is proportional to the output load
impedance, R
OUT
. It is almost constant for PGA1 = high
and for any PGA0, PGA2, PGA3 state. When PGA1 = low,
the output noise floor is 2.7dB lower (see Typical Perfor-
mance Characteristics).
Other Linearity Considerations
LT5514 linearity is a strong function of signal frequency.
OIP3 decreases about 13dB for every octave of frequency
increase above 100MHz.
As noted in the Circuit Operation section, at any given
frequency and input level, the LT5514 provides a current
output with fairly constant intermodulation distortion fig-
ure in dBc, regardless of the output load value. For higher
R
OUT
values, more gain and output power is available, and
better OIP3 figures can be achieved. However, high R
OUT
values are not easily implemented in practice, limited by
the availability of high ratio output impedance transforma-
tion networks.
Linearity can also be limited by the output RC time con-
stant (bandwidth limitations), particularly for high R
OUT
values. A solution is outlined in the Bandpass Applications
section.
The LT5514 linearity degrades when common mode sig-
nal is present. The input transformer center tap should be
decoupled to ground to provide a balanced input differen-
tial signal and to avoid linearity degradation for high
attenuation steps. When the signal frequency is lower than
50MHz, and there is significant common mode signal,
then high attenuation settings may result in degraded
linearity.
At signal frequencies below 100MHz, the LT5514’s inter-
nal linearity compensation circuitry may provide “sweet
spots” with very high OIP3, in excess of +60dBm. This
almost perfect distortion correction cannot be sustained
over the full operating temperature range and with varia-
tions of the LT5514 output load (complex impedance
Z
OUT
). Users are advised to rely on data shown in the
Typical Performance Characteristics curves to estimate
the dependable linearity performance.
Wideband Applications
At low frequencies, the value of the decoupling capacitors,
choke inductors and choice of transformer will set the
minimum frequency of operation. Output DC coupling is
possible, but this typically reduces the LT5514’s output
DC bias voltage, and thus the output swing and available
power.
At high frequencies, the output RC time constants set an
upper limit to the maximum frequency of operation in the
case of the wideband output networks presented so far.
For example the LT5514 output capacitance, C
OUT
= 1.9pF,
and a pure resistive load, R
OUT
= 200
, will set the –3dB
bandwidth to about 400MHz. In an actual application, the
R
LOAD
C
LOAD
product may be even more restrictive. The
use of wideband output networks will not only limit the
bandwidth, but will also degrade linearity because part of
the available power is wasted driving the capacitive load.
The LT5514’s output reactance is capacitive. Therefore
improved AC response is possible by using external series
output inductors. When driving purely resistive loads, an
inductor in series with the LT5514 output may help to
achieve maximally flat AC response as exemplified in the
characterization setup schematic (Figure 9).
APPLICATIU
W
U
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| LT5514EFE#PBF | 功能描述:IC IF AMP/ADC DRVR PROG 20TSSOP RoHS:是 類(lèi)別:RF/IF 和 RFID >> RF 其它 IC 和模塊 系列:- 標(biāo)準(zhǔn)包裝:100 系列:* |
| LT5514EFE#TR | 功能描述:IC IF AMP/ADC DRVR PROG 20TSSOP RoHS:否 類(lèi)別:RF/IF 和 RFID >> RF 其它 IC 和模塊 系列:- 標(biāo)準(zhǔn)包裝:100 系列:* |
| LT5514EFE#TRPBF | 功能描述:IC IF AMP/ADC DRVR PROG 20TSSOP RoHS:是 類(lèi)別:RF/IF 和 RFID >> RF 其它 IC 和模塊 系列:- 標(biāo)準(zhǔn)包裝:100 系列:* |
| LT5515 | 制造商:LINER 制造商全稱(chēng):Linear Technology 功能描述:800MHz to 2.7GHz High Linearity Direct Conversion Quadrature Demodulator |
| LT5515EUF | 功能描述:IC DEMODULATOR QUADRATURE 16-QFN RoHS:否 類(lèi)別:RF/IF 和 RFID >> RF 解調(diào)器 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:- 功能:解調(diào)器 LO 頻率:- RF 頻率:70MHz ~ 300MHz P1dB:-9dBm 增益:- 噪音數(shù)據(jù):6.36dB 電流 - 電源:41.5mA 電源電壓:2.7 V 封裝/外殼:28-WFQFN 裸露焊盤(pán) 供應(yīng)商設(shè)備封裝:28-TQFN-EP（5x5） 包裝:帶卷 (TR) |
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