97-8004167 07-14-17
Information subject to change
29
7224 & 7226 OPERATOR’S MANUAL –
SECTION 6
Once an approximate Rc and Cc have been
computed, these values will need to be evaluated.
To do this, install components with the required
values in the main board at locations R82 and C25
as shown in
Figure 6.10.
Figure 6.10 – Custom Compensation Location
If a change in compensation is necessary, an ad
-
justment to the resistor component of the Compen-
sation circuit is probably required.
If the output current waveform is ringing, the circuit
is underdamped: You have too much gain and
should lower the resistance (see
Figure 6.12
).
Figure 6.11 – Compensation Effects on Waveform
If the output current waveform is neither un-
derdamped or overdamped, but the top of the
squarewave is not level, then you should instead
decrease the capacitor value (see
Figure 6.14
).
Figure 6.12 – Square Wave Showing a
Decrease in R is Required
When making adjustments:
Resistor:
Increase or decrease resistance values
in increments of +/- 10%.
Capacitor:
Incrementally decrease capacitor val-
ues by a factor of 2 or 3.
Figure 6.13 – Square Wave Showing an
Increase in R is Required
Figure 6.14 – Square Wave Showing a
Decrease in C is Required
STEP 7: Optimizing the Compensation Values.
If the output current waveform is rounded, the
circuit is overdamped: You have too little gain and
should increase resistance (see
Figure 6.13
).
Remember the load you are connecting is a
part of the system and the amplifier should not
be turned on without the load being connected.
After installing the components, check to ensure
that jumper J5 is correctly installed (see
STEP 4
),
then power up the amplifier without signal input.
To begin testing, input a square wave with a fre
-
quency of 100 Hz to 1 kHz, or a squared pulse at a
low level (typically 0.25 to 2.0 volts). A limited-rise-
time, repetitive pulse of low duty cycle is preferred.
Observe the output current through a current
monitor or current probe. Look for clean transition
edges. The presence of ringing or rounding on the
transition edges indicates compensation problems.
(See
Figure 6.11
.)
