參數(shù)資料
型號(hào)： OPA820ID
英文描述： Unity-Gain Stable, Low-Noise, Voltage-Feedback Operational Amplifier
中文描述： 單位增益穩(wěn)定，低噪聲，電壓反饋運(yùn)算放大器
文件頁(yè)數(shù)： 17/25頁(yè)
文件大?。?/td> 427K
代理商： OPA820ID
"#$
SBOS303A JUNE 2004 REVISED JULY 2004
www.ti.com
17
OPA820
HighSpeed
DAC
V
O
= I
D
R
F
R
F
C
F
GBP
→
Gain Bandwidth
Product (Hz) for the OPA820.
C
D
I
D
I
D
Figure 8. Wideband, Low-Distortion DAC
Transimpedance Amplifier
The DC gain for this circuit is equal to R
F
. At high frequencies,
the DAC output capacitance (C
D
) will produce a zero in the
noise gain for the OPA820 that may cause peaking in the
closed-loop frequency response. C
F
is added across R
F
to
compensate for this noise-gain peaking. To achieve a flat
transimpedance frequency response, this pole in the
feedback network should be set to:
1
2 R
F
C
F
GBP
4 R
F
C
D
which will give a corner frequency f
3dB
of approximately:
f
3dB
GBP
2 R
F
C
D
ACTIVE FILTERS
Most active filter topologies will have exceptional performance
using the broad bandwidth and unity-gain stability of the
OPA820. Topologies employing capacitive feedback require
a unity-gain stable, voltage-feedback op amp. Sallen-Key
filters simply use the op amp as a noninverting gain stage
inside an RC network. Either current- or voltage-feedback op
amps may be used in Sallen-Key implementations.
Figure 9 shows an example Sallen-Key low-pass filter, in
which the OPA820 is set up to deliver a low-frequency gain of
+2. The filter component values have been selected to
achieve a maximally-flat Butterworth response with a 5MHz,
3dB bandwidth. The resistor values have been slightly
adjusted to compensate for the effects of the 240MHz
bandwidth provided by the OPA820 in this configuration. This
filter may be combined with the ADC driver suggestions to
provide moderate (2-pole) Nyquist filtering, limiting noise, and
out-of-band harmonics into the input of an ADC. This filter will
deliver the exceptionally low harmonic distortion required by
high SFDR ADCs such as the ADS850 (14-bit, 10MSPS,
82dB SFDR).
OPA820
+5V
5V
R
2
505
C
150pF
R
1
124
V
O
V
1
R
G
402
R
F
402
C
100pF
Powersupply
decoupling not shown.
Figure 9. 5MHz Butterworth Low-Pass Active
Filter
Another type of filter, a high-Q bandpass filter, is shown in
Figure 10. The transfer function for this filter is:
V
OUT
V
IN
s
R3
R1R4C1
R4
s
2
s
1
R1C1
R3
R2R4R5C1C2
with
O
2
R
3
R
2
R
4
R
5
C
1
C
2
and
O
Q
1
R
1
C
1
For the values chosen in Figure 10:
f
O
w
O
2
1MHz
and
Q = 100
See Figure 11 for the frequency response of the filter
shown in Figure 10.
OPA820
OPA820
V
OUT
R
3
500
R
4
500
R
5
158
C
2
1000pF
R
1
15.8k
R
2
158
V
IN
C
1000pF
Figure 10. High-Q 1MHz Bandpass Filter
(1)
(2)
(3)
(4)
(5)
(6)
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
OPA820ID 制造商:Texas Instruments 功能描述:Operational Amplifier (Op-Amp) IC 制造商:Texas Instruments 功能描述:IC, OP-AMP, 280MHZ, 240V/ us, SOIC-8
OPA820IDBVR 功能描述:高速運(yùn)算放大器 Unity Gain Stable Lo Noise Vltg Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)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(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube
OPA820IDBVRG4 功能描述:高速運(yùn)算放大器 Unity Gain Stable Lo Noise Vltg Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)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(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube
OPA820IDBVT 功能描述:高速運(yùn)算放大器 Unity Gain Stable Lo Noise Vltg Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)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(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube
OPA820IDBVTG4 功能描述:高速運(yùn)算放大器 Unity Gain Stable Lo Noise Vltg Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)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(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube
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