OPERATIONAL POWER SUPPLY

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

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

electrically

instead

of

using

a

tachometer.

In

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.

DS008704-19

DS008704-20

DS008704-21

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