- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄363780 > OPA643U Wideband Low Distortion, High Gain OPERATIONAL AMPLIFIER PDF資料下載
參數(shù)資料
| 型號： | OPA643U |
| 英文描述： | Wideband Low Distortion, High Gain OPERATIONAL AMPLIFIER |
| 中文描述： | 寬帶低失真，高增益運算放大器 |
| 文件頁數(shù)： | 15/17頁 |
| 文件大小： | 262K |
| 代理商： | OPA643U |
OPA643
15
R
F
1k
±200mV Output Adjustment
= – R
G
Supply Decoupling
Not Shown
5k
5k
200
0.1μF
R
G
250
V
I
20k
10k
0.1μF
–5V
+5V
OPA643
+5V
–5V
V
O
V
O
V
I
R
F
Operating junction temperature (T
J
) is given by T
A
+ P
D
θ
JA
. The total internal power dissipation (P
D
) is the sum of
quiescent power (P
DQ
) and additional power dissipated in
the output stage (P
DL
) to deliver load power. Quiescent
power is simply the specified no-load supply current times
the total supply voltage across the part. P
DL
will depend on
the required output signal and load but would, for a grounded
resistive load, be at a maximum when the output is fixed at
a voltage equal to 1/2 either supply voltage (for equal bipolar
supplies). Under this condition P
DL
= V
S2
/(4 R
L
) where R
L
includes feedback network loading.
Note that it is the power in the output stage and not into the
load that determines internal power dissipation.
As a worst case example, compute the maximum T
J
using an
OPA643N (SOT23-5 package) in the circuit of Figure 1
operating at the maximum specified ambient temperature of
+85
°
C. P
D
= 10V 26mA + 5
2
/(4 (100
|| 502
)) =
335mW. Maximum T
J
= +85
°
C + (0.335
150
°
C/W) =
135
°
C.
BOARD LAYOUT GUIDELINES
Achieving optimum performance with a high frequency
amplifier like the OPA643 requires careful attention to
board layout parasitics and external component types.
Recommendations that will optimize performance include:
a)
Minimize parasitic capacitance
to any AC ground for
all of the signal I/O pins. Parasitic capacitance on the
output and inverting input pins can cause instability; on
the non-inverting input, it can react with the source
impedance to cause unintentional bandlimiting. To reduce
unwanted capacitance, a window around the signal I/O
pins should be opened in all of the ground and power
planes around those pins. Otherwise, ground and power
planes should be unbroken elsewhere on the board.
FIGURE 10. DC Coupled, Inverting Gain of –4, with
Output Offset Adjustment.
b)
Minimize the distance
(< 0.25") from the power supply
pins to high frequency 0.1
μ
F decoupling capacitors. At
the device pins, the ground and power plane layout
should not be in close proximity to the signal I/O pins.
Avoid narrow power and ground traces to minimize
inductance between the pins and the decoupling capacitors.
The primary power supply connections (on pins 4 and 7)
should always be decoupled with these capacitors.
Optional output stage power supply connections on pins
5 and 8 may be used to get a slight improvement in
harmonic distortion and settling time (for the 8-pin
packaged parts). Place additional 0.1
μ
F decoupling
capacitors very near to these pins to improve performance.
Larger (2.2
μ
F to 6.8
μ
F) decoupling capacitors, effective
at lower frequency, should also be used on the main
supply pins. These may be placed somewhat farther from
the device and may be shared among several devices in
the same area of the PC board.
c)
Careful selection and placement of external
components will preserve the high frequency
performance of the OPA643.
Resistors should be a very
low reactance type. Surface mount resistors work best
and allow tighter overall layout. Metal film and carbon
composition axially leaded resistors can also provide
good high frequency performance. Again, keep their
leads and PC board trace length as short as possible.
Never use wirewound type resistors in a high frequency
application. Since the output pin and inverting input pin
are the most sensitive to parasitic capacitance, always
position the feedback and series output resistor, if any, as
close as possible to the output pin. Other network
components, such as non-inverting input termination
resistors, should also be placed close to the package.
Where double side component mounting is allowed,
place the feedback resistor directly under the package on
the other side of the board between the output and
inverting input pins. Even with a low parasitic capacitance
shunting the external resistors, excessively high resistor
values can create significant time constants that can
degrade performance. Good axial metal film or surface
mount resistors have approximately 0.2pF in shunt with
the resistor. For resistor values > 1.5k
, this parasitic
capacitance can add a pole and/or zero below 500MHz
that can effect circuit operation. Keep resistor values as
low as possible consistent with load driving considerations.
The 402
feedback used in the typical performance
specifications is a good starting point for design.
d)
Connections to other wideband devices
on the board
may be made with short direct traces or through on-board
transmission lines. For short connections, consider the
trace and the input to the next device as a lumped
capacitive load. Relatively wide traces (50 to 100mils)
should be used, preferably with ground and power planes
opened up around them. Estimate the total capacitive load
and set R
S
from the plot of recommended R
S
vs Capacitive
Load. Low parasitic capacitive loads (< 5pF) may not
need an R
S
since the OPA643 is nominally compensated
to operate with a 2pF parasitic load. Higher parasitic
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| OPA643NB | Wideband Low Distortion, High Gain OPERATIONAL AMPLIFIER |
| OPA643UB | Wideband Low Distortion, High Gain OPERATIONAL AMPLIFIER |
| OPA646 | Low Power, Wide Bandwidth OPERATIONAL AMPLIFIER |
| OPA646U | Low Power, Wide Bandwidth OPERATIONAL AMPLIFIER |
| OPA650 | Wideband, Low Power Voltage Feedback OPERATIONAL AMPLIFIER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA643UB | 制造商:Rochester Electronics LLC 功能描述:HIGH SPEED OP AMP - Bulk |
| OPA644 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:OPA644 - DISCONTINUED PRODUCT. No longer recommended for new design. |
| OPA644U | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| OPA644UB | 制造商:BB 制造商全稱:BB 功能描述:Low Distortion Current Feedback OPERATIONAL AMPLIFIER |
| OPA646 | 制造商:BB 制造商全稱:BB 功能描述:Low Power, Wide Bandwidth OPERATIONAL AMPLIFIER |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。