AE Techron 7800 Series Operation Manual page 34

STEP 7: Optimizing the Compensation Values
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 the Operation DIP switch (SW#1) is set to
Current mode, 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 5.13.)
Figure 5.13 – Compensation Effects on Waveform
If a change in compensation is necessary, an adjust-
ment to the resistor component of the Compensation
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 5.14).
Figure 5.14 – Square Wave Showing a
Decrease in R is Required
34
If the output current waveform is rounded, the
circuit is overdamped: You have too little gain and
should increase resistance (see Figure 5.15).
Figure 5.15 – Square Wave Showing an
If the output current waveform is neither under-
damped or overdamped, but the top of the square-
wave is not level, then you should instead increase
the capacitor value (see Figure 5.16).
Figure 5.16 – Square Wave Showing an
When making adjustments:
Resistor: Increase or decrease resistance values
in increments of +/- 10%.
Capacitor: Incrementally increase capacitor val-
ues by a factor of 2 or 3.
After final adjustments have been made to the
circuit, the final waveform for your planned appli-
cation should be tested to confirm the amplifier's
compensation setting.
NOTE:
• If possible, use 1% metal film resistors. AE
Techron discourages installation of potentiome-
ters in the resistor location of the compensation
circuit because this can decrease stability and
may increase inductance.
• The parallel capacitor in the RC network serves
to increase stability but can be removed, if it is
not required for system stability. If the parallel
capacitor is used, it will usually decrease the
value of resistance needed.
• In multiple amplifier systems, expect to decrease
the value of R63 in series systems by 1/2.
Information subject to change
7800 SERIES OPERATION – SECTION 5
Increase in R is Required
Increase in C is Required
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