參數(shù)資料
型號(hào)： OPA4684IPWT
英文描述： Quad, Low-Power, Current-Feedback OPERATIONAL AMPLIFIER
中文描述： 四，低功耗，電流反饋運(yùn)算放大器
文件頁數(shù)： 12/26頁
文件大?。?/td> 455K
代理商： OPA4684IPWT
OPA4684
SBOS240B
12
www.ti.com
APPLICATIONS INFORMATION
LOW-POWER CURRENT-FEEDBACK OPERATION
The quad-channel OPA4684 gives a new level of perfor-
mance in low-power current-feedback op amps. Using a new
input stage buffer architecture, the OPA4684 CFB
PLUS
ampli-
fier holds nearly constant AC performance over a wide gain
range. This closed-loop internal buffer gives a very low and
linearized impedance at the inverting node, isolating the
amplifier
’
s AC performance from gain element variations.
This allows both the bandwidth and distortion to remain
nearly constant over gain, moving closer to the ideal current
feedback performance of gain bandwidth independence.
This low-power amplifier also delivers exceptional output
power
—
it
’
s
±
4V swing on
±
5V supplies with > 100mA output
drive gives excellent performance into standard video loads
or doubly-terminated 50
cables. Single +5V supply opera-
tion is also supported with similar bandwidths but with re-
duced output power capability. For lower quiescent power in
a CFB
PLUS
amplifier, consider the OPA683 family; while for
higher output power, consider the OPA691 family.
Figure 1 shows the DC-coupled, gain of +2, dual power-
supply circuit used as the basis of the
±
5V Electrical and
Typical Characteristics for each channel. For test purposes,
the input impedance is set to 50
with a resistor to ground
and the output impedance is set to 50
with a series output
resistor. Voltage swings reported in the Electrical Character-
istics are taken directly at the input and output pins while load
powers (dBm) are defined at a matched 50
load. For
the circuit of Figure 1, the total effective load will be
100
|| 1600
= 94
. Gain changes are most easily accom-
plished by simply resetting the R
G
value, holding R
F
constant
at its recommended value of 800
.
mode signal across the input stage, the slew rate for inverting
operation is typically higher and the distortion performance is
slightly improved. An additional input resistor, R
M
, is included
in Figure 2 to set the input impedance equal to 50
. The
parallel combination of R
M
and R
G
set the input impedance.
As the desired gain increases for the inverting configuration,
R
G
is adjusted to achieved the desired gain, while R
M
is also
adjusted to hold a 50
input match. A point will be reached
where R
G
will equal 50
, R
M
is removed, and the input match
is set by R
G
only. With R
G
fixed to achieve an input match to
50
, increasing R
F
will increase the gain. This will, however,
quickly reduce the achievable bandwidth as the feedback
resistor increases from its recommended value of 800
. If
the source does not require an input match to 50
, either
adjust R
M
to get the desired load, or remove it and let the R
G
resistor alone provide the input load.
R
F
800
1/4
OPA4684
+5V
–
5V
50
R
M
50
R
G
800
50
Source
50
Load
V
I
0.1
μ
F
6.8
μ
F
0.1
μ
F
6.8
μ
F
+
+
FIGURE 1. DC-Coupled, G = +2V/V, Bipolar Supply Speci-
fications and Test Circuit.
Figure 2 shows the DC-coupled, gain of
–
1V/V, dual power-
supply circuit used as the basis of the Inverting Typical
Characteristics for each channel. Inverting operation offers
several performance benefits. Since there is no common-
R
F
800
1/4
OPA4684
+5V
–
5V
50
R
53.6
R
G
800
50
Load
50
Source
0.1
μ
F
6.8
μ
F
0.1
μ
F
6.8
μ
F
+
+
V
I
FIGURE 2. DC-Coupled, G =
–
1V/V, Bipolar Supply Specifi-
cations and Test Circuit.
These circuits show
±
5V operation. The same circuits can be
applied with bipolar supplies from
±
2.5V to
±
6V. Internal
supply independent biasing gives nearly the same perfor-
mance for the OPA4684 over this wide range of supplies.
Generally, the optimum feedback resistor value (for nomi-
nally flat frequency response at G = +2) will increase in value
as the total supply voltage across the OPA4684 is reduced.
See Figure 3 for the AC-coupled, single +5V supply, gain of
+2V/V circuit configuration used as a basis for the +5V only
Electrical and Typical Characteristics for each channel. The
key requirement of broadband single-supply operation is to
maintain input and output signal swings within the usable
voltage ranges at both the input and the output. The circuit
of Figure 3 establishes an input midpoint bias using a simple
resistive divider from the +5V supply (two 10k
resistors) to
the noninverting input. The input signal is then AC-coupled
into this midpoint voltage bias. The input voltage can swing
to within 1.25V of either supply pin, giving a 2.5Vp-p input
signal range centered between the supply pins. The input
impedance of Figure 3 is set to give a 50
input match. If the
source does not require a 50
match, remove this and drive
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
OPA4684IPWTG4 功能描述:高速運(yùn)算放大器 Quad Low-Power Current 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
OPA4684M 制造商:TI 制造商全稱:Texas Instruments 功能描述:QUAD LOW-POWER CURRENT-FEEDBACK OPERATIONAL AMPLIFIER
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