PA97DR 데이터 시트보기 (PDF) - Cirrus Logic
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PA97DR Datasheet PDF : 6 Pages
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PA97DR
GENERAL
Please read the “General Operating Considerations” section, which covers stability, supplies, heatsinking, mount-
ing, current limit, SOA interpretation, and specification interpretation. Additional information can be found in the ap-
plication notes. For information on the package outline, heatsinks, and mounting hardware, consult the “Accessory
and Package Mechanical Data” section of the handbook.
CURRENT LIMIT
The PA97DR has no provision for current limiting the output.
COMMON MODE INPUT RANGE
Operational amplifiers are usually designed to have a common mode input voltage range that approximates the
power supply voltage range. However, to keep the cost as low as possible and still meet the requirements of most
applications the common mode input voltage range of the PA97DR is restricted. The input pins must always be a
least 30V from either supply voltage but never more than 500V. This means that the PA97 cannot be used in ap-
plications where the supply voltages are extremely unbalanced. For example, supply voltages of +800V and –100V
would not be allowed in an application where the non-inverting pin is grounded because in normal operation both
input pins would be at 0V and the difference voltage between the positive supply and the input pins would be 800V.
In this kind of application, however, supply voltages +500V and -100V does meet the input common mode voltage
range requirements since the maximum difference voltage between the inputs pins and the supply voltage is 500V
(the maximum allowed). The output has no such restrictions on its voltage swing. The output can swing within 24V
of either supply voltage regardless of value so long as the total supply voltage does not exceed 900V.
INPUT PROTECTION
Although the PA97DR can withstand differential input voltages up to ±20V,
additional external protection is recommended. In most applications 1N4148
or 1N914 signal diodes are sufficient (D1, D2 in Figure 2a). In more de- "
manding applications where low leakage or low capacitance are of concern
2N4416 or 2N5457-2N5459 JFETs connected as diodes will be required (Q1,
Q2 in Figure 2b). In either case the input differential voltage will be clamped
to ±.7V. This is sufficient overdrive to produce maximum power bandwidth.
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Note that this protection does not automatically protect the amplifier from
excessive common mode input voltages.
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POWER SUPPLY PROTECTION
Unidirectional zener diode transient suppressors are recommended as pro-
tection on the supply pins. The zeners clamp transients to voltages within
the power supply rating and also clamp power supply reversals to ground.
Whether the zeners are used or not, the system power supply should be
evaluated for transient performance including power-on overshoot and pow-
er-off polarity reversal as well as line regulation.
Conditions which can cause open circuits or polarity reversals on either pow-
er supply rail should be avoided or protected against. Reversals or opens on
the negative supply rail is known to induce input stage failure. Unidirectional
transzorbs prevent this, and it is desirable that they be both electrically and
physically as close to the amplifier as possible.
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FIGURE 2.
EXTERNAL COMPONENTS
The compensation capacitor Cc must be rated for the total supply voltage. 10pF NPO (COG)capacitor rated at 1kV
is recommended.
Of equal importance is the voltage rating and voltage coefficient of the gain setting feedback resistor. Typical volt-
age ratings of low wattage resistors are 150 to 250V. Up to 900 V can appear across the feedback resistor. High
voltage rated resistors can be obtained. However a 1 megohm feedback resistor composed of five 200k resistors in
series will produce the proper voltage rating.
PA97DRU
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