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參數(shù)資料
| 型號： | OPA657 |
| 元件分類： | 運動控制電子 |
| 英文描述： | Precision, High-Speed Transimpedance Amplifier |
| 中文描述： | 精密，高速互阻抗放大器 |
| 文件頁數(shù)： | 12/18頁 |
| 文件大?。?/td> | 362K |
| 代理商： | OPA657 |
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SBOS291E NOVEMBER 2003 REVISED NOVEMBER 2004
www.ti.com
12
TRANSIMPEDANCE BANDWIDTH AND
NOISE
Limiting the gain set by R
F
can decrease the noise
occurring at the output of the transimpedance circuit.
However, all required gain should occur in the
transimpedance stage, since adding gain after the
transimpedance amplifier generally produces poorer
noise performance. The noise spectral density
produced by R
F
increases with the square-root of R
F
,
whereas the signal increases linearly. Therefore,
signal-to-noise ratio is improved when all the required
gain is placed in the transimpedance stage.
Total noise increases with increased bandwidth. Limit
the circuit bandwidth to only that required. Use a
capacitor, C
F
, across the feedback resistor, R
F
, to limit
bandwidth, even if not required for stability if total output
noise is a concern.
Figure 6a shows the transimpedance circuit without any
feedback capacitor. The resulting transimpedance gain
of this circuit is shown in Figure 7. The –3dB point is
approximately 10MHz. Adding a 16pF feedback
capacitor (Figure 6b) will limit the bandwidth and result
in a –3dB point at approximately 1MHz (seen in
Figure 7). Output noise will be further reduced by
adding a filter (R
FILTER
and C
FILTER
) to create a second
pole (Figure 6c). This second pole is placed within the
feedback loop to maintain the amplifier’s low output
impedance. (If the pole was placed outside the
feedback loop, an additional buffer would be required
and would inadvertently increase noise and dc error).
Using R
DIODE
to represent the equivalent diode
resistance, and C
TOT
for equivalent diode capacitance
plus OPA380 input capacitance, the noise zero, f
Z
, is
calculated by:
f
Z
R
DIODE
R
F
2 R
DIODE
R
F
C
TOT
C
F
OPA380
V
OUT
V
BIAS
R
F
= 10k
(a)
λ
C
STRAY
=0.2pF
C
F
= 16pF
OPA380
V
OUT
V
BIAS
R
F
= 10k
(b)
λ
C
STRAY
=0.2pF
V
OUT
C
= 796pF
R
= 100
C
F
= 21pF
OPA380
V
BIAS
R
F
= 10k
(c)
λ
C
STRAY
= 0.2pF
Figure 6. Transimpedance circuit configurations
with varying total and integrated noise gain
(3)
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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 制造商:Texas Instruments 功能描述:OP AMP, 1.6GHZ FET IP, SMD, SOT235 制造商:Texas Instruments 功能描述:OP AMP, 1.6GHZ FET IP, SMD, SOT235; Op Amp Type:Low Noise; No. of Amplifiers:1; Slew Rate:700V/s; Supply Voltage Range:10V to 12V, 6V; Amplifier Case Style:SOT-23; No. of Pins:5; Bandwidth:350MHz; Operating Temperature Min:-40C; |
| 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 |
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