參數(shù)資料
型號(hào)： OPA604
英文描述： FET-Input, Low Distortion OPERATIONAL AMPLIFIER
中文描述： FET輸入，低失真運(yùn)算放大器
文件頁(yè)數(shù)： 12/12頁(yè)
文件大?。?/td> 178K
代理商： OPA604
12
OPA604
1
00
1
I
(mA)
0
5
log
(V
O
)
1
Frequency (kHz)
2
3
4
f
O
2f
O
3f
O
4f
O
5f
O
V
BE
= 1kHz + DC Bias
V
BE
(V)
0.65
FFT
1
01
0
–I
(mA)
0
5
log
(V
O
)
1
Frequency (kHz)
2
3
4
f
O
2f
O
3f
O
4f
O
5f
O
V
GS
= 1kHz + DC Bias
V
GS
(V)
FFT
V
O
I
D
V
GS
V
O
I
C
V
BE
FIGURE 10. I-V and Spectral Response of NPN and
JFET.
THE OPA604 DESIGN
The OPA604 uses FETs throughout the signal path,
including the input stage, input-stage load, and the
important phase-splitting section of the output stage.
Bipolar transistors are used where their attributes,
such as current capability are important, and where
their transfer characteristics have minimal impact.
The topology consists of a single folded-cascode gain
stage followed by a unity-gain output stage. Differen-
tial input transistors J
1
and J
2
are special large-geom-
etry, P-channel JFETs. Input stage current is a rela-
tively high 800
μ
A, providing high transconductance
and reducing voltage noise. Laser trimming of stage
currents and careful attention to symmetry yields a
nearly symmetrical slew rate of
±
25V/
μ
s.
The JFET input stage holds input bias current to
approximately 50pA or roughly 3000 times lower
than common bipolar-input audio op amps. This dra-
matically reduces noise with high-impedance circuitry.
The drains of J
1
and J
2
are cascoded by Q
1
and Q
2
,
driving the input stage loads, FETs J
3
and J
4
. Distor-
tion reduction circuitry (patented) linearizes the open-
loop response and increases voltage gain. The 20MHz
bandwidth of the OPA604 further reduces distortion
through the user-connected feedback loop.
The output stage consists of a JFET phase-splitter
loaded into high speed all-NPN output drivers. Output
transistors are biased by a special circuit to prevent
cutoff, even with full output swing into 600
loads.
The following discussion is provided, recognizing that
not all measured performance behavior explains or
correlates with listening tests by audio experts. The
design of the OPA604 included consideration of both
objective performance measurements, as well as an
awareness of widely held theory on the success and
failure of previous op amp designs.
SOUND QUALITY
The sound quality of an op amp is often the crucial
selection criteria—even when a data sheet claims ex-
ceptional distortion performance. By its nature, sound
quality is subjective. Furthermore, results of listening
tests can vary depending on application and circuit
configuration. Even experienced listeners in controlled
tests often reach different conclusions.
Many audio experts believe that the sound quality of a
high performance FET op amp is superior to that of
bipolar op amps. A possible reason for this is that
bipolar designs generate greater odd-order harmonics
than FETs. To the human ear, odd-order harmonics
have long been identified as sounding more unpleasant
than even-order harmonics. FETs, like vacuum tubes,
have a square-law I-V transfer function which is more
linear than the exponential transfer function of a bipo-
lar transistor. As a direct result of this square-law
characteristic, FETs produce predominantly even-or-
der harmonics. Figure 10 shows the transfer function
of a bipolar transistor and FET. Fourier transformation
of both transfer functions reveals the lower odd-order
harmonics of the FET amplifier stage.
SOUND QUALITY
Distortion
Rejection
Circuitry
(+)
(–)
Output
Stage
R
3
1k
R
4
1k
R
8
3k
R
9
3k
R
1
75
R
2
75
R
5
500
R
7
4k
R
6
500
I
1
800μA
J
1
J
2
J
3
J
4
Q
4
Q
2
Q
3
Q
1
J
5
I
2
200μA
R
10
10k
R
11
10k
相關(guān)PDF資料
PDF描述
OPA604AP FET-Input, Low Distortion OPERATIONAL AMPLIFIER
OPA604AU FET-Input, Low Distortion OPERATIONAL AMPLIFIER
OPA606 Wide-Bandwidth Difet OPERATIONAL AMPLIFIER
OPA606KM END COVER;
OPA606KP Wide-Bandwidth Difet OPERATIONAL AMPLIFIER
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
OPA604_07 制造商:TI 制造商全稱:Texas Instruments 功能描述:FET-Input, Low Distortion OPERATIONAL AMPLIFIER
OPA604AP 功能描述:音頻放大器 FET-Input Audio Op Amp RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel
OPA604AP 制造商:BURR-BROWN 功能描述:IC OP AMP LOW DISTORTION FET 604 制造商:Texas Instruments 功能描述:Operational Amplifier (Op-Amp) IC
OPA604APG4 功能描述:音頻放大器 FET-Input Audio Op Amp RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel
OPA604AU 功能描述:音頻放大器 FET-Input Audio Op Amp RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel
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