PA96(2005) Ver la hoja de datos (PDF) - Apex Microtechnology
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PA96 Datasheet PDF : 4 Pages
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PA96
OPERATING
CONSIDERATIONS
GENERAL
Please read Application Note 1 “General Operating Con-
siderations” which covers stability, supplies, heat sinking,
mounting, current limit, SOA interpretation, and specification
interpretation. Visit www.apexmicrotech.com for design tools
that help automate tasks such as calculations for stability,
internal power dissipation, current limit, heat sink selection,
Apex’s Application Notes library, Technical Seminar Workbook,
and Evaluation Kits.
SPECIAL PRECAUTIONS
The PA96 operates with up 300V rail to rail voltage, and
delivers amperes of current. Precautions should be taken for
the safety of the user and the amplifier.
Although the non-operating common mode input range is rail
to rail, the differential input voltage must not exceed ±15 V.
Therefore; if the feedback ratio is less than 10, even if
caused by disconnecting a signal source , typical power turn
on transients can destroy the amplifier.
Similarly in a voltage follower application a large differential
transient can be generated if the slew rate of the input is greater
than that of the voltage follower.
Therefore it is prudent to clamp the input with series back
to back diodes as shown below.
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If experimentally optimizing the compensation capacitor,
turn off the supplies and let them bleed to low voltage before
installing each new value. Otherwise internal current pulses of
up to 3 amps can be induced. Also, do you want your fingers
around 300V?
Essentially the full rail to rail power supply voltage may be
applied to the compensation capacitor. A 400V COG or Mica
capacitor is recommended.
POWER BANDWIDTH
The power bandwidth is 1/(π x the negative edge slew time).
The slew time is determined by the compensation capacitor,
load, and internal device capacitance; it is independent of
closed loop gain. The uncompensated power bandwidth is
typically 100kHz for a 250Vp-p output signal into 100Ω. It typi-
cally increases to above 300KHz with no load.
COMPENSATION TABLE
The following table tabulates recommended compensation
capacitor values vs. gain. These values will typically result in
less than 2% overshoot and a -3db small signal bandwidth of
greater than 1MHz, except under operating conditions where
uncompensated gain bandwidth is too low to support a 1MHz
bandwidth. (See gain bandwidth vs. Plus power supply curves).
Note that other factors such as capacitance in parallel with
the feedback resistor may reduce circuit bandwidth from that
determined from the gain bandwidth curve.
Cc
150pf
51pf
33pf
22pf
10pf
5pf
None
Inverting Gain
From
To
1
2
2
5
5
10
10
20
20
50
50
100
100
up
Cc
330 pf
150pf
51pf
33pf
22pf
10pf
5pf
None
Non-Inverting Gain
From
To
1
2
2
3
3
6
6
10
10
20
20
50
50
100
100
up
CURRENT LIMIT
For proper operation the current limit resistor, Rcl, must
be connected as shown in the external connections diagram.
The minimum value is 0.2Ω, with a maximum practical value of
100Ω. For optimum reliability the resistor should be set as high
as possible. The value is calculated as IL = 0.68V/Rcl. Note that
the 0.68V is reduced by 2mV every °C rise in temperature.
Also note that the current limit can be set such that the SOA
is exceeded on a continuous basis. As an example if the current
limit was set at 1.5A and the supply was at 150V, a short to
ground would produce 225 watts internal dissipation, greatly
exceeding the 83 watt steady state SOA rating.
Under some conditions of load and compensation the am-
plifier may oscillate at a low level when current limit is active,
even though the amplifier is stable otherwise. The current
will be limited to the programmed value in this situation. To
minimize such occurrences, use a non-reactive resistor to
program current limit.
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PA96U REV B DECEMBER 2005 © 2005 Apex Microtechnology Corp.
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