MSK801_15 Datasheet, PDF (4/6 Pages) M.S. Kennedy Corporation – 10 MHz full power bandwidth min.

APPLICATION NOTES CON'T
Slew Rate vs. Slew Rate Limit
SLEW RATE:
S=2πfVp; Slew rate is based upon the sinusoidal
linear response of the amplifier and is calculated from
the full power bandwidth frequency.
SLEW RATE LIMIT
dv/dt; The slew rate limit is based upon the amplifier's
response to a step input and is measured between 10%
and 90%. MSK measures Tr or Tf, whichever is greater
at ±10VOUT, RL=100Ω.
Definition of Settling Time
The time required for the output to come within a prede-
termined error band after application of a full scale step
input. This includes the time of delay, slew time and the
small signal settling of the amplifier.
Measuring Settling Time
The only accurate method of measuring settling time is by
the creation of a false summing junction and observing the
error band at that point.
The reasons for not using other methods are as follows:
Observation of settling at the actual summing junction adds
probe capacitance to the input and changes the entire re-
sponse of the system. (Probe capacitance almost doubles
the capacitance at the summing point.) Observing the out-
put is extremely difficult, as the 3% linearity of oscillo-
scopes, and reading inaccuracies, lead to a possible 5%
error. The false summing junction approach works well
bcause the amplifier is subtracting the output from the in-
put, and only 1/2 the actual error appears there.
False Summing Junction Circuit
Offset Null
Typically the MSK 801 has an input offset voltage of
less than ±1 mV. If it is desirable to "null" the offset volt-
age, the circuit below is recommended.
RP=10KΩ
Output Short Circuit Protection
The collectors of the output devices have been brought
out to pins 10 and 12 for short circuit protection, if desired.
A resistor can be inserted between +VC and +VCC pins,
and -VC and -VCC respectively. Resistor values can be se-
lected as follows:
RSC ≅ (+)VCC = (-)VCC
(+)ISC (-)ISC
The addition of the these resistors reduces output volt-
age swing. Decoupling at ±VC can help to retain full swing
for transient pulses.
Problems: Because the amplifier is to be overdriven, 1/2
the input voltage can be expected to appear at the false
summing junction. Therefore, it is necessary to clamp that
point with diodes to limit the voltage excursion to avoid
overdriving the oscilloscope with the consequent recovery
time of the scope itself. The scope probe has capacitance
which significantly affects the settling time measurement.
Keep the associated resistors as low as possible to mini-
mize the RC time constants, and take into account the added
time created by the false summing junction. On the ranges
used for settling time measurement even the best real-time
scopes suffer from reduced bandwidth and relatively slow
For normal operation and best overall response, short
+VCC and +VC and short -VCC and -VC together.
settling; a sampling scope is convenient for these measure-
ments.
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Rev. D 9/06