LM12CL National Semiconductor, LM12CL Datasheet - Page 9

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

Application Information
OPERATIONAL POWER SUPPLY
Note: Supply voltages for the LM318s are
External current limit can be provided for a power op amp as shown above. The positive and negative current limits can be set
precisely and independently. Fast response is assured by D
eters R
an operational power supply or voltage-programmable power source.
SERVO AMPLIFIERS
When making servo systems with a power op amp, there is
a temptation to use it for frequency shaping to stabilize the
servo loop. Sometimes this works; other times there are bet-
ter ways; and occasionally it just doesn’t fly. Usually it’s a
matter of how quickly and to what accuracy the servo must
stabilize.
This motor/tachometer servo gives an output speed propor-
tional to input voltage. A low-level op amp is used for fre-
quency shaping while the power op amp provides current
3
and R
7
. Alternately, the limit can be programmed from a voltage supplied to R
±
15V
(Continued)
DS008704-20
1
and D
9
2
drive to the motor. Current drive eliminates loop phase shift
due to motor inductance and makes high-performance ser-
vos easier to stabilize.
This position servo uses an op amp to develop the rate sig-
nal
high-performance servos, rate signals must be developed
with large error signals well beyond saturation of the motor
drive. Using a separate op amp with a feedback clamp al-
lows the rate signal to be developed properly with position
errors more than an order of magnitude beyond the
loop-saturation level as long as the photodiode sensors are
positioned with this in mind.
. Adjustment range can be set down to zero with potentiom-
electrically
instead
2
and R
6
of
. This is the set up required for
DS008704-19
using
DS008704-21
a
tachometer.
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