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參數(shù)資料
| 型號(hào)： | OPA2658UB |
| 元件分類(lèi)： | 運(yùn)算放大器 |
| 英文描述： | Dual Wideband, Low Power, Current Feedback OPERATIONAL AMPLIFIER |
| 中文描述： | 雙寬帶，低功耗，電流反饋運(yùn)算放大器 |
| 文件頁(yè)數(shù)： | 11/13頁(yè) |
| 文件大?。?/td> | 230K |
| 代理商： | OPA2658UB |
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11
OPA2658
CAPACITIVE LOADS
The OPA2658’s output stage has been optimized to drive
low resistive loads. Capacitive loads, however, will decrease
the amplifier’s phase margin which may cause high fre-
quency peaking or oscillations. Capacitive loads greater than
5pF should be buffered by connecting a small resistance,
usually 10
to 35
, in series with the output as shown in
Figure 5. This is particularly important when driving high
capacitance loads such as flash A/D converters.
In general, capacitive loads should be minimized for opti-
mum high frequency performance. Coax lines can be driven
if the cable is properly terminated. The capacitance of coax
cable (29pF/foot for RG-58) will not load the amplifier
when the coaxial cable or transmission line is terminated
with its characteristic impedance.
COMPENSATION
The OPA2658 is internally compensated and is stable in
unity gain with a phase margin of approximately 62
°
, and
approximately 64
°
in a gain of +2V/V when used with the
recommended feedback resistor value. Frequency response
for other gains are shown in the Typical Performance Curves.
The high-frequency response of the OPA2658 in a good
layout is very flat with frequency.
DISTORTION
The OPA2658’s Harmonic Distortion characteristics into a
100
load are shown versus frequency and power output in
the Typical Performance Curves. Distortion can be further
improved by increasing the load resistance as illustrated in
Figure 6. Remember to include the contribution of the
feedback resistance when calculating the effective load re-
sistance seen by the amplifier.
Narrowband communication channel requirements will ben-
efit from the OPA2658’s wide bandwidth and low
intermodulation distortion on low quiescent power. If output
signal power at two closely spaced frequencies is required,
third-order nonlinearities in any amplifier will cause spuri-
ous power at frequencies very near the two funda-
mental frequencies. If the two test frequencies, f
1
and f
2
,
are specified in terms of average and delta frequency,
f
O
= (f
1
+ f
2
)/2 and
f =
f
2
– f
1
, the two, third-order,
close-in spurious tones will appear at f
O
±
3
f. The two
FIGURE 5. Driving Capacitive Loads.
C
L
R
L
50
R
S
10
to 35
402
402
1/2
OPA2658
tone, third-order spurious plot shown in Figure 7 indicates
how far below these two equal power, closely spaced, tones
the intermodulation spurious will be. The single tone power
is at a matched 50
load. The unique design of the OPA2658
provides much greater spurious free range than what a two-
tone third-order intermodulation intercept specification would
predict. This can be seen in Figure 7 as the spurious free
range actually increases at the higher output power levels.
–55
–60
–65
–70
–75
–80
–85
5MHz HARMONIC DISTORTION vs
LOAD RESISTANCE (G = +2)
Load Resistance (
)
H
10
100
1k
G = +2, V
O
= 2Vp-p, f
O
= 5MHz
3f
O
2f
O
FIGURE 6. 5MHz Harmonic Distortion vs Load Resistance.
–65
–70
–75
–80
–85
–90
–18 –16 –14 –12 –10
–8
–6
–4
–2
0
2
4
T
TWO TONE, THIRD-ORDER SPURIOUS LEVELS
Single Tone Power (dBm)
20MHz
10MHz
5MHz
CROSSTALK
Crosstalk is the undesired result of the signal of one channel
mixing with and reproducing itself in the output of the other
channel. Crosstalk occurs in most multichannel integrated
circuits. In dual devices, the effect of crosstalk is measured by
driving one channel and observing the output of the undriven
channel over various frequencies. The magnitude of this effect
is referenced in terms of channel- to-channel isolation and
expressed in decibels. "Input referred" points to the fact that
there is a direct correlation between gain and crosstalk, there-
fore at increased gain, crosstalk also increases by a factor
equal to that of the gain. Figure 8 illustrates the measured
effect of crosstalk in the OPA2658U.
FIGURE 7. Third-Order Intercept Point vs Frequency.
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| OPA2670IRGVT | 功能描述:高速運(yùn)算放大器 Sgl PortHi Out Crnt VDSL2 Line Driver 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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