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參數(shù)資料
| 型號： | OPA657N |
| 廠商： | Texas Instruments, Inc. |
| 英文描述： | 1.6GHz, Low-Noise, FET-Input OPERATIONAL AMPLIFIER |
| 中文描述： | 1.6GHz的，低噪聲，F(xiàn)ET輸入運算放大器 |
| 文件頁數(shù)： | 11/18頁 |
| 文件大小： | 362K |
| 代理商： | OPA657N |
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SBOS291E NOVEMBER 2003 REVISED NOVEMBER 2004
www.ti.com
11
BIASING PHOTODIODES IN SINGLE-SUPPLY
CIRCUITS
The +IN input can be biased with a positive DC voltage
to offset the output voltage and allow the amplifier
output to indicate a true
zero
photodiode measurement
when the photodiode is not exposed to any light. It will
also prevent the added delay that results from coming
out of the negative rail. This bias voltage appears
across the photodiode, providing a reverse bias for
faster operation. An RC filter placed at this bias point will
reduce noise. (Refer to Figure 4.) This bias voltage can
also serve as an offset bias point for an ADC with range
that does not include ground.
OPA380
V
OUT
100k
V+
R
F
10M
C
F(1)
< 1pF
0.1
μ
F
λ
NOTE: (1) C
is optional to prevent gain peaking.
It includes the stray capacitance of R
F
.
+V
Bias
Figure 4. Filtered reverse bias voltage
TRANSIMPEDANCE AMPLIFIER
Wide bandwidth, low input bias current, and low input
voltage and current noise make the OPA380 an ideal
wideband photodiode transimpedance amplifier. Low
voltage noise is important because photodiode
capacitance causes the effective noise gain of the
circuit to increase at high frequency.
The key elements to a transimpedance design are
shown in Figure 5:
the total input capacitance (C
TOT
), consisting of the
photodiode capacitance (C
DIODE
) plus the parasitic
common-mode
and
capacitance (3pF + 1.1pF for the OPA380);
differential-mode
input
the desired transimpedance gain (R
F
);
the Gain Bandwidth Product (GBW) for the
OPA380 (90MHz).
With these three variables set, the feedback capacitor
value (C
F
) can be set to control the frequency response.
C
STRAY
is the stray capacitance of R
F
, which is 0.2pF for
a typical surface-mount resistor.
To achieve a maximally flat 2nd-order Butterworth
frequency response, the feedback pole should be set
to:
1
2 R
F
C
F
C
STRAY
GBW
4 R
F
C
TOT
Bandwidth is calculated by:
f
3dB
GBW
2 R
F
C
TOT
Hz
These
transimpedance
transimpedance bandwidth, the high-speed CMOS
OPA300 (180MHz GBW), or the OPA656 (230MHz
GBW) may be used.
For additional information, refer to Application Bulletin
AB050 (SBOA055),
Compensate Transimpedance
Amplifiers Intuitively
, available for download at
www.ti.com
.
equations
will
result
in
even
maximum
higher
bandwidth.
For
C
TOT(3)
OPA380
V
OUT
5V
10M
+5V
R
F
C
F(1)
C
STRAY(2)
λ
NOTE: (1) C
F
is optional to prevent gainpeaking.
(2) C
is the stray capacitance of R
(typically, 0.2pF for a surfacemount resistor).
(3) C
is the photodiode capacitance plus OPA380
input capacitance.
R
(optional
pulldownresistor)
Figure 5. Transimpedance Amplifier
(1)
(2)
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| OPA657N | 制造商:Texas Instruments 功能描述:OP AMP 1.6GHZ FET IP SMD SOT235 |
| OPA657N/250 | 功能描述:高速運算放大器 1.6GHz Low Noise FET-Input Op 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 |
| OPA657N/250G4 | 功能描述:高速運算放大器 1.6GHz Low Noise FET-Input Op 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 |
| OPA657N/3K | 制造商:TI 制造商全稱:Texas Instruments 功能描述:1.6GHz, Low-Noise, FET-Input OPERATIONAL AMPLIFIER |
| OPA657NB | 制造商:Texas Instruments 功能描述:OP AMP 1.6GHZ FET IP SMD SOT235 |
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