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| 型號： | OPA832IDR |
| 英文描述： | Low-Power, Single-Supply, Fixed-Gain Video Buffer Amplifier |
| 中文描述： | 低功耗，單電源，固定增益視頻緩沖放大器 |
| 文件頁數(shù)： | 18/26頁 |
| 文件大小： | 471K |
| 代理商： | OPA832IDR |
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SBOS266B JUNE 2003 REVISED SEPTEMBER 2004
www.ti.com
18
and/or distortion, the simplest and most effective solution
is to isolate the capacitive load from the feedback loop by
inserting a series isolation resistor between the amplifier
output and the capacitive load.
The Typical Characteristic curves show the recommended
R
S
versus capacitive load and the resulting frequency
response at the load. Parasitic capacitive loads greater
than 2pF can begin to degrade the performance of the
OPA832. Long PC board traces, unmatched cables, and
connections to multiple devices can easily exceed this
value. Always consider this effect carefully, and add the
recommended series resistor as close as possible to the
output pin (see the
Board Layout Guidelines
section).
The criterion for setting this R
S
resistor is a 1dB peaked
frequency response at the load. Increasing the noise gain
will also reduce the peaking (see Figure 7).
DISTORTION PERFORMANCE
The OPA832 provides good distortion performance into a
150
load. Relative to alternative solutions, it provides
exceptional performance into lighter loads and/or
operating on a single +3.3V supply. Generally, until the
fundamental signal reaches very high frequency or power
levels, the 2nd-harmonic will dominate the distortion with
a negligible 3rd-harmonic component. Focusing then on
the 2nd-harmonic, increasing the load impedance
improves distortion directly. Remember that the total load
includes the feedback network; in the noninverting
configuration (see Figure 3) this is sum of R
F
+ R
G
, while
in the inverting configuration, only R
F
needs to be included
in parallel with the actual load.
Figure 9 shows the 2nd- and 3rd-harmonic distortion
versus supply voltage. In order to maintain the input signal
within
acceptable
operating
common-mode voltage is adjusted for each supply
voltage. For example, the common-mode voltage is +2V
for a single +5V supply, and the distortion is 66.5dBc for
the 2nd-harmonic and 74.6dBc for the 3rd-harmonic.
range,
the
input
66
67
68
69
70
71
72
73
74
75
76
Supply Voltage (V)
H
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
C
5
6
7
8
9
10
11
G= +2V/V
R
L
= 500
V
= 2V
PP
f = 5MHz
CommonMode Voltage
Right Scale
2ndHarmonic
Left Scale
3rdHarmonic
Left Scale
Figure 9. 5MHz Harmonic Distortion vs Supply
Voltage
NOISE PERFORMANCE
Unity-gain stable, rail-to-rail (RR) output, voltage-feed-
back op amps usually show a higher input noise voltage.
The 9.2nV/
√
Hz input voltage noise for the OPA832
however, is much lower than comparable amplifiers. The
input-referred voltage noise and the two input-referred
current noise terms (2.8pA/
√
Hz) combine to give low
output noise under a wide variety of operating conditions.
Figure 10 shows the op amp noise analysis model with all
the noise terms included. In this model, all noise terms are
taken to be noise voltage or current density terms in either
nV/
√
Hz or pA/
√
Hz.
4kT
R
G
R
G
R
F
R
S
OPA832
I
BI
E
O
I
BN
4kT = 1.6E
20J
at 290 K
E
RS
E
NI
4kTR
S
√
4kTR
F
√
Figure 10. Noise Analysis Model
The total output spot noise voltage can be computed as the
square root of the sum of all squared output noise voltage
contributors. Equation 1 shows the general form for the
output noise voltage using the terms shown in Figure 10:
E
O
E
NI
2
I
BN
R
S
2
4kTR
S
NG
2
I
BI
R
F
2
4kTR
F
NG
Dividing
(NG = (1 + R
F
/R
G
)) will give the equivalent input-referred
spot noise voltage at the noninverting input, as shown in
Equation 2:
this
expression
by
the
noise
gain
E
N
E
NI
2
I
BN
R
S
2
4kTR
S
I
BI
R
F
NG
2
4kTR
F
NG
Evaluating these two equations for the circuit and
component values shown in Figure 1 will give a total output
spot noise voltage of 19.3nV/
√
Hz and a total equivalent
input spot noise voltage of 9.65nV/
√
Hz. This is including
the noise added by the resistors. This total input-referred
spot noise voltage is not much higher than the 9.2nV/
√
Hz
specification for the op amp voltage noise alone.
(1)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA832IDRG4 | 功能描述:視頻放大器 Lo-Pwr Single-Supply Fixed-Gain Video Bfr RoHS:否 制造商:ON Semiconductor 通道數(shù)量:4 電源類型: 工作電源電壓:3.3 V, 5 V 電源電流: 最小工作溫度: 最大工作溫度: 封裝 / 箱體:TSSOP-14 封裝:Reel |
| OPA835 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Ultra Low-Power, Rail-to-Rail Out, Negative Rail In, VFB Op Amp |
| OPA835_1110 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Ultra Low-Power, Rail-to-Rail Out, Negative Rail In, VFB Op Amp |
| OPA835_12 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Ultra Low-Power, Rail-to-Rail Out, Negative Rail In, VFB Op Amp |
| OPA835IDBVEVM | 功能描述:放大器 IC 開發(fā)工具 OPA835 in DBV pckg EVM RoHS:否 制造商:International Rectifier 產(chǎn)品:Demonstration Boards 類型:Power Amplifiers 工具用于評估:IR4302 工作電源電壓:13 V to 23 V |
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