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| 型號(hào)： | OPA635 |
| 英文描述： | Wideband, Single Supply OPERATIONAL AMPLIFIERS |
| 中文描述： | 寬帶，單電源運(yùn)算放大器 |
| 文件頁(yè)數(shù)： | 12/17頁(yè) |
| 文件大?。?/td> | 179K |
| 代理商： | OPA635 |
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12
OPA634, OPA635
The front page circuit is a good example of this type of
application. It was designed to take V
IN
between 0V and
0.5V, and produce V
OUT
between 1V and 2V, when using a
+3V supply. This means G = 2.00, and
V
OUT
= 1.50V – G
0.25V = 1.00V. Plugging into the above equations gives:
NG = 2.33, R
1
= 375
, R
2
= 2.25k
, and R
3
= 563
. The
resistors were changed to the nearest standard values.
NON-INVERTING AMPLIFIER WITH
REDUCED PEAKING
Figure 4 shows a non-inverting amplifier that reduces peak-
ing at low gains. The resistor R
C
compensates the OPA634
or OPA635 to have higher Noise Gain (NG), which reduces
the AC response peaking (typically 5dB at G = +1 without
R
C
) without changing the DC gain. V
IN
needs to be a low
impedance source, such as an op amp. The resistor values
are low to reduce noise. Using both R
T
and R
F
helps
minimize the impact of parasitic impedances.
A unity gain buffer can be designed by selecting R
T
= R
F
=
20.0
and R
C
= 40.2
(do not use R
G
). This gives a Noise
Gain of 2, so its response will be similar to the Characteris-
tics Plots with G = +2. Decreasing R
C
to 20.0
will increase
the Noise Gain to 3, which typically gives a flat frequency
response, but with less bandwidth.
The circuit in Figure 1 can be redesigned to have less
peaking by increasing the noise gain to 3. This is accom-
plished by adding R
C
= 2.55k
between the op amps inputs.
DESIGN-IN TOOLS
DEMONSTRATION BOARDS
Two PC boards are available to assist in the initial evaluation
of circuit performance using the OPA634 and OPA635 in
their three package styles. These are available free as an
unpopulated PC board delivered with descriptive documen-
tation. The summary information for these boards is shown
below:
OPA63x
+V
S
V
OUT
V
IN
R
3
R
2
R
1
R
4
FIGURE 3. DC Level-Shifting Circuit.
OPA63x
V
OUT
V
IN
R
G
R
T
R
F
R
C
FIGURE 4. Compensated Non-Inverting Amplifier.
The Noise Gain can be calculated as follows:
Contact the Burr-Brown Applications support line to request
any of these boards.
OPERATING SUGGESTIONS
OPTIMIZING RESISTOR VALUES
Since the OPA634 and OPA635 are voltage feedback op
amps, a wide range of resistor values may be used for the
feedback and gain setting resistors. The primary limits on
these values are set by dynamic range (noise and distortion)
and parasitic capacitance considerations. For a non-inverting
unity gain follower application, the feedback connection
should be made with a 25
resistor, not a direct short (see
Figure 4). This will isolate the inverting input capacitance
from the output pin and improve the frequency response
flatness. Usually, for G > 1 application, the feedback resistor
value should be between 200
and 1.5k
. Below 200
, the
feedback network will present additional output loading
which can degrade the harmonic distortion performance.
Above 1.5k
, the typical parasitic capacitance (approxi-
mately 0.2pF) across the feedback resistor may cause unin-
tentional band-limiting in the amplifier response.
A good rule of thumb is to target the parallel combination of
R
F
and R
G
(Figure 1) to be less than approximately 400
.
The combined impedance R
F
|| R
G
interacts with the invert-
ing input capacitance, placing an additional pole in the
feedback network and thus, a zero in the forward response.
Assuming a 3pF total parasitic on the inverting node, hold-
ing R
F
|| R
G
<400
will keep this pole above 130MHz. By
BOARD
PART
NUMBER
LITERATURE
REQUEST
NUMBER
PRODUCT
PACKAGE
OPA63xU
OPA63xN
8-Pin SO-8
5-Pin SOT23-5
6-Pin SOT23-6
DEM-OPA68xU
DEM-OPA6xxN
MKT-351
MKT-348
G
R
R
R
G
R
R
G
NG
G G
F
G
T
F
C
1
2
1
2
1
1
= +
= +
+
=
/
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| OPA634N | ECONOLINE: RB & RA - Dual Output from a Single Input Rail- Power Sharing on Output- Industry Standard Pinout- 1kVDC & 2kVDC Isolation- Custom Solutions Available- UL94V-0 Package Material- Efficiency to 85% |
| OPA634U | Wideband, Single Supply OPERATIONAL AMPLIFIERS |
| OPA635N | Wideband, Single Supply OPERATIONAL AMPLIFIERS |
| OPA635U | Wideband, Single Supply OPERATIONAL AMPLIFIERS |
| OPA634 | Wideband, Single Supply OPERATIONAL AMPLIFIERS |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA635N | 制造商:BB 制造商全稱:BB 功能描述:Wideband, Single Supply OPERATIONAL AMPLIFIERS |
| OPA635N/250 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| OPA635N/3K | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Voltage-Feedback Operational Amplifier |
| OPA635U | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| OPA635U/2K5 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Voltage-Feedback Operational Amplifier |
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