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參數(shù)資料
| 型號： | OPA694IDR |
| 英文描述： | Wideband, Low-Power, Current Feedback Operational Amplifier |
| 中文描述： | 寬帶，低功耗，電流反饋運算放大器 |
| 文件頁數(shù)： | 12/24頁 |
| 文件大?。?/td> | 382K |
| 代理商： | OPA694IDR |
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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
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA694IDRG4 | 功能描述:高速運算放大器 WideBand Low-Power Curr Feedback Amp 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 |
| OPA695 | 制造商:BB 制造商全稱:BB 功能描述:Wideband, Low-Power, Current Feedback Operational Amplifier |
| OPA695ID | 功能描述:高速運算放大器 Ultra-Wideband 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 |
| OPA695ID | 制造商:Texas Instruments 功能描述:IC SM OP-AMP WIDEBAND CFB |
| OPA695IDBVR | 功能描述:高速運算放大器 Ultra-Wideband 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 |
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