SGM2324 sg-micro, SGM2324 Datasheet - Page 7

• Manufacturer Part Number: SGM2324
• Description: 1mhz, Quad, General Purpose Cmos Operational Amplifier
• Manufacturer: sg-micro

APPLICATION NOTES
Driving Capacitive Loads
The SGM2324 can directly drive 250pF in unity-gain without
oscillation. The unity-gain follower (buffer) is the most sensitive
configuration to capacitive loading. Direct capacitive loading
reduces the phase margin of amplifiers and this results in ringing
or even oscillation. Applications that require greater capacitive
drive capability should use an isolation resistor between the
output and the capacitive load like the circuit in Figure 1. The
isolation resistor R
increase stability. The bigger the R
stable V
accuracy because R
An improvement circuit is shown in Figure 2, It provides DC
accuracy as well as AC stability. R
connecting the inverting signal with the output, C
to counteract the loss of phase margin by feeding the high
frequency component of the output signal back to the amplifier’s
inverting input, thereby preserving phase margin in the overall
feedback loop.
Figure 2. Indirectly Driving Heavy Capacitive Load with DC
Accuracy
For no-buffer configuration, there are two others ways to
increase the phase margin: (a) by increasing the amplifier’s gain
or (b) by placing a capacitor in parallel with the feedback resistor
to counteract the parasitic capacitance associated with inverting
node.
V
Figure 1. Indirectly Driving Heavy Capacitive Load
IN
V
IN
OUT
¼
will be. Note that this method results in a loss of gain
C
SGM2324
¼
F
SGM2324
ISO
ISO
and the load capacitor C
forms a voltage divider with the R
R
ISO
C
L
R
F
provides the DC accuracy by
ISO
ISO
R
F
resistor value, the more
R
C
L
L
L
V
F
V
form a zero to
and R
OUT
OUT
Iso
LOAD
serve
.
7
Power-Supply Bypassing and Layout
The SGM2324 operates from a single +3V to +5.5V supply or
dual ±1.5V to ±2.75V supplies. For single-supply operation,
bypass the power supply V
which should be placed close to the V
operation, both the V
bypassed to ground with separate 0.1µF ceramic capacitors.
2.2µF tantalum capacitor can be added for better performance.
Vn
Vp
¼
V
Figure 3. Amplifier with Bypass Capacitors
V
DD
SGM2324
SS
(GND)
0.1µF
10µF
DD
V
OUT
and the V
DD
with a 0.1µF ceramic capacitor
Vn
Vp
SS
DD
¼
V
SGM2324
supplies should be
pin. For dual-supply
DD
SGM2324
V
SS
0.1µF
0.1µF
10µF
10µF
V
OUT