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FEATURES
• LOW THERMAL RESISTANCE — 1.4°C/W
• CURRENT FOLDOVER PROTECTION — NEW
• HIGH TEMPERATURE VERSION — PA12H
• EXCELLENT LINEARITY — Class A/B Output
• WIDE SUPPLY RANGE — ±10V to ±50V
• HIGH OUTPUT CURRENT — Up to ±15A Peak
APPLICATIONS
• MOTOR, VALVE AND ACTUATOR CONTROL
• MAGNETIC DEFLECTION CIRCUITS UP TO 10A
• POWER TRANSDUCERS UP TO 100kHz
• TEMPERATURE CONTROL UP TO 360W
• PROGRAMMABLE POWER SUPPLIES UP TO 90V
• AUDIO AMPLIFIERS UP TO 120W RMS
DESCRIPTION
The PA12 is a state of the art high voltage, very high
output current operational amplifier designed to drive resis-
tive, inductive and capacitive loads. For optimum linearity,
especially at low levels, the output stage is biased for class
A/B operation using a thermistor compensated base-emitter
voltage multiplier circuit. The safe operating area (SOA) can
be observed for all operating conditions by selection of user
programmable current limiting resistors. For continuous opera-
tion under load, a heatsink of proper rating is recommended.
The PA12 is not recommended for gains below –3 (inverting)
or +4 (non-inverting).
This hybrid integrated circuit utilizes thick film (cermet)
resistors, ceramic capacitors and semiconductor chips to
maximize reliability, minimize size and give top performance.
Ultrasonically bonded aluminum wires provide reliable inter-
connections at all operating temperatures. The 8-pin TO-3
package is hermetically sealed and electrically isolated. The
use of compressible isolation washers voids the warranty.
EQUIVALENT SCHEMATIC
POWER RATING
Not all vendors use the same method to rate the power han-
dling capability of a Power Op Amp. APEX rates the internal
dissipation, which is consistent with rating methods used by
transistor manufacturers and gives conservative results. Rating
delivered power is highly application dependent and therefore
can be misleading. For example, the 125W internal dissipation
rating of the PA12 could be expressed as an output rating of
250W for audio (sine wave) or as 440W if using a single ended
DC load. Please note that all vendors rate maximum power
using an infinite heatsink.
THERMAL STABILITY
APEX has eliminated the tendency of class A/B output
stages toward thermal runaway and thus has vastly increased
amplifier reliability. This feature, not found in most other Power
Op Amps, was pioneered by APEX in 1981 using thermistors
which assure a negative temperature coefficient in the quies-
cent current. The reliability benefits of this added circuitry far
outweigh the slight increase in component count.
EXTERNAL CONNECTIONS
8-PIN TO-3
PACKAGE STYLE CE
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ABSOLUTE MAXIMUM RATINGS
SPECIFICATIONS
SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS
PA12 PA12A
PARAMETER TEST CONDITIONS 2, 5 MIN TYP MAX MIN TYP MAX UNITS
INPUT
OFFSET VOLTAGE, initial TC = 25°C ±2 ±6 ±1 ±4 mV
OFFSET VOLTAGE, vs. temperature Full temperature range ±10 ±65 * ±40 µV/°C
OFFSET VOLTAGE, vs. supply TC = 25°C ±30 ±200 * * µV/V
OFFSET VOLTAGE, vs. power TC = 25°C ±20 * µV/W
BIAS CURRENT, initial TC = 25°C ±12 ±30 10 20 nA
BIAS CURRENT, vs. temperature Full temperature range ±50 ±500 * * pA/°C
BIAS CURRENT, vs. supply TC = 25°C ±10 * pA/V
OFFSET CURRENT, initial TC = 25°C ±12 ±30 ±5 ±10 nA
OFFSET CURRENT, vs. temperature Full temperature range ±50 * pA/°C
INPUT IMPEDANCE, DC TC = 25°C 200 * MΩ
INPUT CAPACITANCE TC = 25°C 3 * pF
COMMON MODE VOLTAGE RANGE3 Full temperature range ±VS –5 ±VS –3 * * V
COMMON MODE REJECTION, DC Full temp. range, VCM = ±VS –6V 74 100 * * dB
GAIN
OPEN LOOP GAIN at 10Hz TC = 25°C, 1KΩ load 110 * dB
OPEN LOOP GAIN at 10Hz Full temp. range, 8Ω load 96 108 * * dB
GAIN BANDWIDTH PRODUCT @ 1MHz
TC = 25°C, 8Ω load 4 * MHz
POWER BANDWIDTH TC = 25°C, 8Ω load 13 20 * * kHz
PHASE MARGIN, AV = +4 Full temp. range, 8Ω load 20 * °
OUTPUT
VOLTAGE SWING3
TC = 25°C, PA12 = 10A, PA12A = 15A
±VS –6 * V
VOLTAGE SWING3 TC = 25°C, IO = 5A ±VS –5 * V
VOLTAGE SWING3 Full temp. range, IO = 80mA ±VS–5 * V
CURRENT, peak TC = 25°C 10 15 A
SETTLING TIME to .1% TC = 25°C, 2V step 2 * µs
SLEW RATE TC = 25°C 2.5 4 * * V/µs
CAPACITIVE LOAD Full temperature range, AV = 4 1.5 * nF
CAPACITIVE LOAD Full temperature range, AV > 10 SOA *
POWER SUPPLY
VOLTAGE Full temperature range ±10 ±40 ±45 * * ±50 V
CURRENT, quiescent TC = 25°C 25 50 * * mA
THERMAL
RESISTANCE, AC, junction to case4 TC = –55 to +125°C, F > 60Hz .8 .9 * * °C/W
RESISTANCE, DC, junction to case TC = –55 to +125°C 1.25 1.4 * * °C/W
RESISTANCE, junction to air TC = –55 to +125°C 30 * °C/W
TEMPERATURE RANGE, case Meets full range specification –25 +85 –55 +125 °C
PA12 • PA12A
NOTES: * The specification of PA12A is identical to the specification for PA12 in applicable column to the left.
1. Long term operation at the maximum junction temperature will result in reduced product life. Derate internal power dissipation to
achieve high MTTF.
2. The power supply voltage for all tests is ±40, unless otherwise noted as a test condition.
3. +VS and –VS denote the positive and negative supply rail respectively. Total VS is measured from +VS to –VS.
4. Rating applies if the output current alternates between both output transistors at a rate faster than 60Hz.
5. Full temperature range specifications are guaranteed but not 100% tested.
PA12/PA12A
SUPPLY VOLTAGE, +Vs to –Vs 100V
OUTPUT CURRENT, within SOA 15A
POWER DISSIPATION, internal 125W
INPUT VOLTAGE, differential ±VS –3V
INPUT VOLTAGE, common mode ±VS
TEMPERATURE, pin solder -10s 300°C
TEMPERATURE, junction1 200°C
TEMPERATURE RANGE, storage –65 to +150°C
OPERATING TEMPERATURE RANGE, case –55 to +125°C
The internal substrate contains beryllia (BeO). Do not break the seal. If accidentally broken, do not crush, machine, or
subject to temperatures in excess of 850°C to avoid generating toxic fumes.
CAUTION
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TYPICAL PERFORMANCE
GRAPHS PA12 • PA12A
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load and short circuits to the supply rail or common if the
current limits are set as follows at TC = 25°C:
SHORT TO ±VS SHORT TO
±VS C, L, OR EMF LOAD COMMON
50V .30A 2.4A
40V .58A 2.9A
35V .87A 3.7A
30V 1.5A 4.1A
25V 2.4A 4.9A
20V 2.9A 6.3A
15V 4.2A 8.0A
These simplified limits may be exceeded with further analysis
using the operating conditions for a specific application.
CURRENT LIMITING
Refer to Application Note 9, "Current Limiting", for details of
both fixed and foldover current limit operation. Visit the Apex
web site at www.apexmicrotech.com for a copy of the Power
Design spreadsheet (Excel) which plots current limits vs. steady
state SOA. Beware that current limit should be thought of as a
+/–20% function initially and varies about 2:1 over the range
of –55°C to 125°C.
For fixed current limit, leave pin 7 open and use equations
1 and 2.
RCL = 0.65/LCL (1)
ICL = 0.65/RCL (2)
Where:
ICL is the current limit in amperes.
RCL is the current limit resistor in ohms.
For certain applications, foldover current limit adds a slope
to the current limit which allows more power to be delivered
to the load without violating the SOA. For maximum foldover
slope, ground pin 7 and use equations 3 and 4.
0.65 + (Vo * 0.014)
ICL = (3)
RCL
0.65 + (Vo * 0.014)
RCL = (4)
ICL
Where:
Vo is the output voltage in volts.
Most designers start with either equation 1 to set RCL for the
desired current at 0v out, or with equation 4 to set RCL at the
maximum output voltage. Equation 3 should then be used to
plot the resulting foldover limits on the SOA graph. If equa-
tion 3 results in a negative current limit, foldover slope must
be reduced. This can happen when the output voltage is the
opposite polarity of the supply conducting the current.
In applications where a reduced foldover slope is desired,
this can be achieved by adding a resistor (RFO) between pin
7 and ground. Use equations 4 and 5 with this new resistor
in the circuit.
Vo * 0.14
0.65 +
10.14 + RFO
ICL = (5)
RCL
Vo * 0.14
0.65 +
10.14 + RFO
RCL = (6)
ICL
Where:
RFO is in K ohms.
OPERATING
CONSIDERATIONS
PA12 • PA12A
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 complete Application Notes library; Technical Seminar
Workbook; and Evaluation Kits.
SAFE OPERATING AREA (SOA)
The output stage of most power amplifiers has three distinct
limitations:
1. The current handling capability of the transistor geometry
and the wire bonds.
2. The second breakdown effect which occurs whenever the
simultaneous collector current and collector-emitter voltage
exceeds specified limits.
3. The junction temperature of the output transistors.
The SOA curves combine the effect of all limits for this Power
Op Amp. For a given application, the direction and magnitude
of the output current should be calculated or measured and
checked against the SOA curves. This is simple for resistive
loads but more complex for reactive and EMF generating
loads. However, the following guidelines may save extensive
analytical efforts.
1. Capacitive and dynamic* inductive loads up to the following
maximum are safe with the current limits set as specified.
CAPACITIVE LOAD INDUCTIVE LOAD
±VS ILIM = 5A ILIM = 10A ILIM = 5A ILIM = 10A
50V 200µF 125µF 5mH 2.0mH
40V 500µF 350µF 15mH 3.0mH
35V 2.0mF 850µF 50mH 5.0mH
30V 7.0mF 2.5mF 150mH 10mH
25V 25mF 10mF 500mH 20mH
20V 60mF 20mF 1,000mH 30mH
15V 150mF 60mF 2,500mH 50mH
*If the inductive load is driven near steady state conditions,
allowing the output voltage to drop more than 8V below the
supply rail with ILIM = 15A or 25V below the supply rail with ILIM
= 5A while the amplifier is current limiting, the inductor must
be capacitively coupled or the current limit must be lowered
to meet SOA criteria.
2. The amplifier can handle any EMF generating or reactive
This data sheet has been carefully checked and is believed to be reliable, however, no responsibility is assumed for possible inaccuracies or omissions. All specifications are subject to change without notice.
PA12U REV O OCTOBER 2003 © 2003 Apex Microtechnology Corp.
