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參數(shù)資料
| 型號： | OPA678 |
| 英文描述： | Wideband Switched-Input OPERATIONAL AMPLIFIER |
| 中文描述： | 寬帶開關(guān)輸入運算放大器 |
| 文件頁數(shù)： | 8/14頁 |
| 文件大?。?/td> | 279K |
| 代理商： | OPA678 |
OPA678
8
APPLICATION TIPS
Wideband amplifier circuits require good layout techniques
to be successful. The use of short, direct signal paths and
heavy (2oz copper recommended) ground planes are abso-
lutely necessary to achieve the performance level inherent in
the OPA678. Oscillation, ringing, poor bandwidth and set-
tling, gain peaking, and instability are typical problems that
plague all high-speed amplifiers when they are used in poor
layouts. The OPA678 is no different in this respect—any
amplifier with a gain bandwidth product of a few GHz
requires some care be taken in its application.
Points to remember:
1.
Use a heavy copper ground plane on the component side
of your PC board. This provides a low inductance
ground and it also conducts heat from active circuit
package pins into ambient air by convection.
2.
Bypass power supply pins directly at the active device.
The use of monoblock or tantalum capacitors with very
short leads is highly recommended. A 0.1
μ
F in parallel
with a 1.0
μ
F will be optimum in most applications. The
0.1
μ
F should be placed directly at the device’s power
supply leads.
3.
When using the OPA678 in the unity gain voltage
follower configuration it is recommended that a 100
resistor be connected from the output to the inverting
input for optimum performance.
4.
Signal paths should be short and direct. Feedback resis-
tors, compensation capacitors, termination resistors, etc.
should have lead lengths no longer than 1/4 inch (6cm).
5.
Surface mount components (chip resistors, capacitors,
etc.) have low inductance and are therefore recom-
mended. Parasitic inductance and capacitance should be
avoided if best performance is to be achieved.
6.
Resistors used in feedback networks should have values
of a few hundred ohms for best performance. Shunt
capacitance problems limit the acceptable range to about
1k
or on the high resistance end and to a value that is
within the amplifier’s output drive limits on the low
end. Metal film and carbon compensation resistors will
be satisfactory.
7.
Wirewound resistors (even “noninductive” types) are
absolutely unacceptable in high frequency circuits.
Avoid overloading the output. Remember that output
current must be provided by the amplifier to drive its
own feedback network as well as to drive its “l(fā)oad.”
Lowest distortion is achieved with high impedance
loads.
PC board traces for signal and power lines should be
wide to reduce impedance or inductance.
10. Don’t forget that these amplifiers use
±
5V supplies.
Although they will operate perfectly well with +5V and
–5.2V, the use of
±
15V supplies will result in destruc-
tion.
11. Standard commercial test equipment has not been de-
signed to test devices in the OPA678 speed range.
Benchtop op amp testers and ATE systems will require
a special test head to successfully test these amplifiers.
12. High-speed amplifiers can drive only a limited amount
of capacitance. If the load exceeds 10 to 20pF consider
using a fast buffer or a small resistor to isolate the
capacitance from the amplifier’s output. Capacitive loads
will cause loop instability if not compensated for.
13. Terminate transmission line loads. Unterminated lines,
such as coaxial cable, can appear to the amplifier to be
a capacitive or inductive load. By terminating a trans-
mission line with its characteristic impedance, the
amplifier’s load then appears as a purely resistive im-
pedance.
14. For clean, fast input selection the logic input pins
should be terminated with appropriate resistors. Resis-
tors should be connected from input selection pins to
ground plane with short leads. Failure to terminate long
lines will result in ringing and poor high frequency
switching.
15. Plug-in prototype boards and wire-wrap boards will not
be satisfactory. A clean layout using RF techniques is
required; there is no shortcut.
8.
9.
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| OPA680N | Wideband, Voltage Feedback OPERATIONAL AMPLIFIER With Disable TM |
| OPA680P | Wideband, Voltage Feedback OPERATIONAL AMPLIFIER With Disable TM |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA678AP | 制造商:BB 制造商全稱:BB 功能描述:Wideband Switched-Input OPERATIONAL AMPLIFIER |
| OPA678AU | 功能描述:高速運算放大器 Widebane Switched RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補償電壓: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 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| OPA680 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Wideband, Voltage Feedback OPERATIONAL AMPLIFIER With Disable |
| OPA680N | 制造商:BB 制造商全稱:BB 功能描述:Wideband, Voltage Feedback OPERATIONAL AMPLIFIER With Disable TM |
| OPA680N/250 | 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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