參數(shù)資料
型號(hào)： OPA3695
英文描述： Wideband, Low-Power, Current Feedback Operational Amplifier
中文描述： 寬帶，低功耗，電流反饋運(yùn)算放大器
文件頁(yè)數(shù)： 12/24頁(yè)
文件大?。?/td> 382K
代理商： OPA3695
"#$
SBOS319C SEPTEMBER 2004 REVISED NOVEMBER 2004
www.ti.com
12
SAW FILTER BUFFER
One common requirement in an IF strip is to buffer the
output of a mixer with enough gain to recover the insertion
loss of a narrowband SAW filter. Figure 5 shows one
possible configuration driving a SAW filter. The
2-Tone,
3rd-Order Intermodulation Intercept
plot is shown in the
Typical Characteritics curves. Operating in the inverting
mode at a voltage gain of –8V/V, this circuit provides a 50
input match using the gain set resistor, has the feedback
optimized for maximum bandwidth (250MHz in this case),
and drives through a 50
output resistor into the matching
network at the input of the SAW filter. If the SAW filter gives
a 12dB insertion loss, a net gain of 0dB to the 50
load at
the output of the SAW (which could be the input
impedance of the next IF amplifier or mixer) will be
delivered in the passband of the SAW filter. Using the
OPA694 in this application will isolate the first mixer from
the impedance of the SAW filter and provide very low
two-tone, 3rd-order spurious levels in the SAW filter
bandwidth.
OPA694
SAW
Filter
+12V
Matching
Network
= 12dB
(SAW Loss)
50
Source
50
50
P
O
P
O
P
I
400
50
P
I
0.1
μ
F
1000pF
1000pF
5k
5k
Figure 5. IF Amplifier Driving SAW Filter
WIDEBAND UNITY GAIN BUFFER WITH
IMPROVED FLATNESS
The unity gain buffer configuration of Figure 1 shows a
peaking in the frequency response exceeding 2dB. This
gives the slight amount of overshoot and ringing apparent
in the gain of +1V/V pulse response curves. A similar
circuit that holds a flatter frequency response, giving
improved pulse fidelity, is shown in Figure 6.
This circuit removes the peaking by bootstrapping out any
parasitic effects on R
G
. The input impedance is still set by
R
M
as the apparent impedance looking into R
G
is very
high. R
M
may be increased to show a higher input
impedance, but larger values will start to impact DC output
offset voltage. This circuit creates an additional input offset
voltage as the difference in the two input bias currents
times the impedance to ground at V
I
. Figure 7 shows a
comparison of small-signal frequency response for the
unity gain buffer of Figure 1 compared to the improved
approach shown in Figure 6. Either approach gives a
low-power unity-gain buffer with > 1.56GHz bandwidth.
OPA694
+5V
DIS
R
O
50
V
O
R
F
430
R
G
430
R
M
50
5V
V
I
Figure 6. IF Amplifier Driving SAW Filter
3
0
3
6
9
12
N
10M
100M
Frequency (MHz)
3G
1G
G = +1, Figure 1
G = +1, Figure 6
Figure 7. IF Amplifier Driving SAW Filter
相關(guān)PDF資料
PDF描述
OPA694 Wideband, Low-Power, Current Feedback Operational Amplifier
OPA695 Wideband, Low-Power, Current Feedback Operational Amplifier
OPA3684 Wideband, Low-Power, Current Feedback Operational Amplifier
OPA2683 Wideband, Low-Power, Current Feedback Operational Amplifier
OPA2684 Wideband, Low-Power, Current Feedback Operational Amplifier
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
OPA3695EVM 功能描述:放大器 IC 開(kāi)發(fā)工具 OPA3695EVM Eval Mod RoHS:否 制造商:International Rectifier 產(chǎn)品:Demonstration Boards 類(lèi)型:Power Amplifiers 工具用于評(píng)估:IR4302 工作電源電壓:13 V to 23 V
OPA3695IDBQ 功能描述:運(yùn)算放大器 - 運(yùn)放 Ultra-WB Crnt-Feed back Op Amp RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
OPA3695IDBQG4 功能描述:運(yùn)算放大器 - 運(yùn)放 Ultra-WB Current- Feedback Op Amp RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
OPA3695IDBQR 功能描述:運(yùn)算放大器 - 運(yùn)放 Ultra-WB Crnt-Feed back Op Amp RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
OPA3695IDBQRG4 功能描述:運(yùn)算放大器 - 運(yùn)放 Ultra-WB Current- Feedback Op Amp RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
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