OPA501BM BURR-BROWN [Burr-Brown Corporation], OPA501BM Datasheet - Page 6

• Manufacturer Part Number: OPA501BM
• Description: High Current, High Power OPERATIONAL AMPLIFIER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

APPLICATIONS INFORMATION
Grounding techniques can greatly affect the performance of
a power op amp. Figure 1 shows grounds connected so that
load current does not flow through signal ground connec-
tions. Power supply and load connections should be physi-
cally separated from the amplifier input and signal connec-
tions.
Power supply connections to the amplifier should be by-
passed with 10 F tantalum capacitors connected close to the
device pins. The capacitors should be connected to load
ground as shown.
FIGURE 1. Basic Circuit Connections.
CURRENT LIMITS
The OPA501 has independent positive and negative current
limit circuits. Current limits are set by the value of R
R
I
Amperes and R
creases with increasing temperature—see typical perfor-
mance curves. The current limit resistors conduct the full
amplifier output current. Power dissipation of the current
limit resistors at maximum current is:
The current limit resistors can be chosen from a variety of
types. Most wire-wound types are satisfactory, although
some physically large resistors may have excessive induc-
tance which can cause instability.
SAFE OPERATING AREA
Stress on the output transistor is determined by the output
current and the voltage across the conducting output transis-
tor. The power dissipated by the output transistor is equal to
the product of the output current and the voltage across the
conducting transistor, V
LIMIT
–
SC
V
IN
. The approximate value of these resistors is:
is the desired maximum current at room temperature in
R
1
®
OPA501
OPA501
SC
R
is in ohms. The current limit value de-
P
(1)
SC
+
MAX
V–
R
(1)
+
CE
2
I
0.65
. The Safe Operating Area (SOA),
LIMIT
V+
(I
LIMIT
R
R
+
SC
–
SC
0. 0437
)
2
NOTE: (1) 10µF Tantalum.
R
SC
G = 1 +
Load
R
R
2
1
+
SC
and
6
Figure 2, shows the permissible range of voltage and cur-
rent. SOA is reduced at high operating temperature—see
Figure 3.
The safe output current decreases as V
short-circuits are very demanding. A short-circuit to ground
forces the full power supply voltage (positive or negative
side) across the conducting transistor. With V
current limit must be set for 2A to be safe for short-circuit
to ground. For further information on SOA and evaluating
signal and load conditions, consult Applications Bulletin
AB-039.
HEAT SINKING
Most applications require a heat sink to assure that the
maximum junction temperature of 200 C is not exceeded.
The size of the heat sink required depends on the power
dissipated by the amplifier and ambient temperature condi-
tions. Application Bulletin AB-039 explains how to find
maximum power dissipation for DC, AC, reactive loads, and
other conditions. Applications Bulletin AB-038 shows how
to determine heat sink requirements.
The case of the OPA501 is isolated from all circuitry and can
be fastened directly to a heat sink. This eliminates cumber-
some insulating hardware that degrades thermal perfor-
mance. See Applications Bulletin AB-037 for information
on mounting techniques and procedures.
FIGURE 2. Transistor Safe Operating Area at +25 C Case
FIGURE 3. Transistor Safe Operating Area at +125 C Case
1.0
0.8
0.6
0.4
0.2
0.1
1.0
0.8
0.6
0.4
0.2
0.1
10
10
8
6
4
2
8
6
4
2
1
1
T
T
T
T
JC
JC
CASE
JUNCTION
CASE
JUNCTION
Maximum
Temperature.
Specified
Temperature.
Maximum
Specified
Current
= 2.2°C/W
Current
= 2.2°C/W
= +25°C
= +125°C
2
2
= +200°C
= +200°C
Voltage Across Output Transistor (V)
Voltage Across Output Transistor (V)
4
4
DC
6
Maximum
Specified
Voltage
DC
6
5ms
Dissipation
8
8
Breakdown
Power
10
10
Limit
Maximum
Specified
Voltage
Second
Limit
RM, AM
SM, BM
20
20
CE
5ms
RM, AM
SM, BM
increases. Output
40
S
40
= 30V, the
60 80
60 80
0.5ms
0.5ms
1ms
1ms
100
100