Datasheet

OPA336, 2336, 4336
8
SBOS068C
www.ti.com
accuracy. For example, with R
L
= 25kΩ, OPA336 series op
amps perform well with capacitive loads in excess of 1000pF,
as shown in Figure 4. Without R
S
, capacitive load drive is
typically 350pF for these conditions, as shown in Figure 5.
Capacitive Load (pF)
Resistive Load (kΩ)
105 100
10k
1k
100
Operation Above Selected Gain
Curve Not Recommended
G = +1
R
L
to Ground
G = +2
R
L
to Ground
G = +1
R
L
to V
S
/2
V
S
= +5V, V
O
= V
S
/2
FIGURE 4. Small-Signal Step Response Using Series Re-
sistor to Improve Capacitive Load Drive.
Alternatively, the resistor may be connected in series with
the output outside of the feedback loop. However, if there is
a resistive load parallel to the capacitive load, it and the
series resistor create a voltage divider. This introduces a
Direct Current (DC) error at the output; however, this error
may be insignificant. For instance, with R
L
= 100kΩ and
R
S
= 100Ω, there is only about a 0.1% error at the output.
Figure 5 shows the recommended operating regions for the
OPA336. Decreasing the load resistance generally improves
capacitive load drive. Figure 5 also illustrates how stability
differs depending on where the resistive load is connected.
With G = +1 and R
L
= 10kΩ connected to V
S
/2, the OPA336
can typically drive 500pF. Connecting the same load to
ground improves capacitive load drive to 1000pF.
R
S
= 100Ω, Load = 2kΩ || 1000pF, V
S
= +5V
50µs/div
20mV/div
FIGURE 5. Stability—Capacitive Load vs Resistive Load.