5
Application Information
The Intersil HA-2842 is a state of the art monolithic device
which also approaches the “ALL-IN-ONE” amplifier concept.
This device features an outstanding set of AC parameters
augmented by excellent output drive capability providing for
suitable application in both high speed and high output drive
circuits.
Primarily intended to be used in balanced 50
and 75
coaxial cable systems as a driver, the HA-2842 could also be
used as a power booster in audio systems as well as a
power amp in power supply circuits. This device would also
be suitable as a small DC motor driver.
Prototyping Guidelines
For best overall performance in any application, it is
recommended that high frequency layout techniques be
used. This should include:
1. Mounting the device through a ground plane.
2. Connecting unused pins (NC) to the ground plane.
3. Mounting feedback components on Teflon standoffs
and/or locating these components as close to the device
as possible.
4. Placing power supply decoupling capacitors from device
supply pins to ground.
Power Dissipation Considerations
At high output currents, especially with the 8 lead SOIC
package, care must be taken to ensure that the Maximum
Junction Temperature (T
J
, see “Absolute Maximum Ratings”
table) isn’t exceeded. As an example consider the HA-2842
in the SOIC package, with a required output current of 50mA
at V
OUT
= 10V with
±
15V supplies. The power dissipation is
the quiescent power (450mW = 30V x 15mA) plus the power
dissipated in the output stage
(P
OUT
= 250mW = 50mA x (15V- 10V)), or a total of
700mW. The thermal resistance (
θ
JA
) of the SOIC package
is 157
o
C/W, which increases the junction temperature by
110
o
C over the ambient temperature (T
A
). Remaining below
T
JMAX
requires that T
A
be restricted to
≤
40
o
C (150
o
C -
110
o
C). Heatsinking would be required for operation at
ambient temperatures greater than 40
o
C.
Note that the problem isn’t as severe with the PDIP package
due to its lower thermal resistance, however it is
recommended that the above analysis be performed for any
package if operating outside the conditions listed below:
Allowable output power can be increased by decreasing the
quiescent dissipation via lower supply voltages.
For more information please refer to Application Note AN556,
Thermal Safe Operating Areas for High Current Op Amps.
MAX P
OUT
WITHOUT HEATSINK (V
S
=
±
15V)
T
A
8 LEAD PDIP
(
θ
JA
= 92
o
C/W)
8 LEAD SOIC
(
θ
JA
= 157
o
C/W)
85
o
C
260mW
Heatsink Required
70
o
C
420mW
60mW
25
o
C
910mW
350mW
Typical Performance Curves
T
A
= 25
o
C, V
SUPPLY
=
±
15V, R
L
= 1k
,
C
L
< 10pF, Unless Otherwise Specified
FIGURE 1. FREQUENCY RESPONSE FOR VARIOUS GAINS
FIGURE 2. GAIN BANDWIDTH PRODUCT vs SUPPLY VOLTAGE
10
100
1K
10K
100K
1M
10M
100M
FREQUENCY (Hz)
G
120
100
80
60
40
20
0
0
90
180
P
OPEN LOOP
A
VCL
= 1000
A
VCL
= 100
A
VCL
= 10
A
VCL
= 2
OPEN LOOP
A
VCL
= 1000
A
VCL
= 100
A
VCL
= 10
A
VCL
= 2
G
5
6
7
8
9
10
11
12
13
14
15
SUPPLY VOLTAGE (
±
V)
90
80
70
60
50
40
30
100
HA-2842