LM12CL National Semiconductor, LM12CL Datasheet - Page 7

• Manufacturer Part Number: LM12CL
• Description: 80W Operational Amplifier
• Manufacturer: National Semiconductor

Application Information
PARALLEL OPERATION
Output drive beyond the capability of one power amplifier
can be provided as shown here. The power op amps are
wired as followers and connected in parallel with the outputs
coupled
high-voltage op amp is used to provide voltage gain. Overall
feedback compensates for the voltage dropped across the
equalization resistors.
With parallel operation, there may be an increase in un-
loaded supply current related to the offset voltage across the
equalization resistors. More output buffers, with individual
equalization resistors, may be added to meet even higher
drive requirements.
This connection allows increased output capability without
requiring a separate control amplifier. The output buffer, A
provides load current through R
the main amplifier, A
ers can be added.
Current sharing among paralleled amplifiers can be affected
by gain error as the power-bandwidth limit is approached. In
the first circuit, the operating current increase will depend
upon the matching of high-frequency characteristics. In the
second circuit, however, the entire input error of A
across R
power limiting to be activated as the slew limit is ap-
4
through
and R
5
. The supply current increase can cause
equalization
1
, through R
5
4
. Again, more output buff-
equal to that supplied by
resistors.
(Continued)
DS008704-13
A
DS008704-12
2
standard,
appears
2
,
7
proached. This will not damage the LM12. It can be avoided
in both cases by connecting A
restricting bandwidth with C
SINGLE-SUPPLY OPERATION
Although op amps are usually operated from dual supplies,
single-supply operation is practical. This bridge amplifier
supplies bi-directional current drive to a servo motor while
operating from a single positive supply. The output is easily
converted to voltage drive by shorting R
to the output of A
Either input may be grounded, with bi-directional drive pro-
vided to the other. It is also possible to connect one input to
a positive reference, with the input signal varying about this
voltage. If the reference voltage is above 5V, R
not required.
HIGH VOLTAGE AMPLIFIERS
The voltage swing delivered to the load can be doubled by
using the bridge connection shown here. Output clamping to
the supplies can be provided by using a bridge-rectifier as-
sembly.
2
, rather than A
1
.
1
as an inverting amplifier and
1
.
6
and connecting R
DS008704-14
DS008704-15
2
www.national.com
and R
3
are
7