參數(shù)資料
型號(hào)： LOG112
元件分類(lèi)： 跨阻放大器
英文描述： Precision, High-Speed Transimpedance Amplifier
中文描述： 精密，高速互阻抗放大器
文件頁(yè)數(shù)： 11/18頁(yè)
文件大?。?/td> 362K
代理商： LOG112
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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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LOG112AID 功能描述:對(duì)數(shù)放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道數(shù)量:3 帶寬:3 dB 共模抑制比（最小值）: 輸入補(bǔ)償電壓:+/- 7 mV 輸入電壓范圍（最大值）:5.5 V 工作電源電壓:4.5 V to 5.5 V 電源電流:+/- 15 mA 工作溫度范圍:- 40 C to +85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel
LOG112AID 制造商:Texas Instruments 功能描述:IC AMP LOG SMD SOIC14 112
LOG112AIDE4 功能描述:對(duì)數(shù)放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道數(shù)量:3 帶寬:3 dB 共模抑制比（最小值）: 輸入補(bǔ)償電壓:+/- 7 mV 輸入電壓范圍（最大值）:5.5 V 工作電源電壓:4.5 V to 5.5 V 電源電流:+/- 15 mA 工作溫度范圍:- 40 C to +85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel
LOG112AIDR 功能描述:對(duì)數(shù)放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道數(shù)量:3 帶寬:3 dB 共模抑制比（最小值）: 輸入補(bǔ)償電壓:+/- 7 mV 輸入電壓范圍（最大值）:5.5 V 工作電源電壓:4.5 V to 5.5 V 電源電流:+/- 15 mA 工作溫度范圍:- 40 C to +85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel
LOG112AIDRE4 功能描述:對(duì)數(shù)放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道數(shù)量:3 帶寬:3 dB 共模抑制比（最小值）: 輸入補(bǔ)償電壓:+/- 7 mV 輸入電壓范圍（最大值）:5.5 V 工作電源電壓:4.5 V to 5.5 V 電源電流:+/- 15 mA 工作溫度范圍:- 40 C to +85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel
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