Normally, input bias current is approximately 1pA. How-
ever, input voltages exceeding the power supplies can
cause excessive current to flow in or out of the input pins.
Momentary voltages greater than the power supply can be
tolerated as long as the current on the input pins is limited
to 10mA. This is easily accomplished with an input resis-
tor, as shown in Figure 2.
APPLICATIONS INFORMATION
OPA336 series op amps are fabricated on a state-of-the-art
0.6 micron CMOS process. They are unity-gain stable and
suitable for a wide range of general-purpose applications.
Power-supply pins should be bypassed with 0.01µF ceramic
capacitors. OPA336 series op amps are protected against
reverse battery voltages.
OPERATING VOLTAGE
+5V
OPA336 series op amps can operate from a +2.1V to +5.5V
single supply with excellent performance. Most behavior
remains unchanged throughout the full operating voltage
range. Parameters which vary significantly with operating
voltage are shown in the typical characteristics. OPA336
series op amps are fully specified for operation from +2.3V
to +5.5V; a single limit applies over the supply range. In
addition, many parameters are ensured over the specified
temperature range, –40°C to +85°C.
IOVERLOAD
10mA max
VOUT
OPAx336
VIN
5kΩ
FIGURE 2. Input Current Protection for Voltages Exceeding
the Supply Voltage.
CAPACITIVE LOAD AND STABILITY
OPA336 series op amps can drive a wide range of capaci-
tive loads. However, all op amps under certain conditions
may become unstable. Op-amp configuration, gain, and
load value are just a few of the factors to consider when
determining stability.
INPUT VOLTAGE
The input common-mode range of OPA336 series op amps
extends from (V–) – 0.2V to (V+) – 1V. For normal
operation, inputs should be limited to this range. The
absolute maximum input voltage is 300mV beyond the
supplies. Thus, inputs greater than the input
common-mode range but less than maximum input volt-
age, while not valid, will not cause any damage to the op
amp. Furthermore, the inputs may go beyond the power
supplies without phase inversion, as shown in Figure 1,
unlike some other op amps.
When properly configured, OPA336 series op amps can
drive approximately 10,000pF. An op amp in unity-gain
configuration is the most vulnerable to capacitive load. The
capacitive load reacts with the op amp’s output resistance,
along with any additional load resistance, to create a pole in
the response which degrades the phase margin. In unity gain,
OPA336 series op amps perform well with a pure capacitive
load up to about 300pF. Increasing gain enhances the
amplifier’s ability to drive loads beyond this level.
One method of improving capacitive load drive in the
unity-gain configuration is to insert a 50Ω to 100Ω resistor
inside the feedback loop, as shown in Figure 3. This reduces
ringing with large capacitive loads while maintaining DC
6V
VOUT
RS
100Ω
OPAx336
VOUT
0V
VIN
CL
RL
FIGURE 1. No Phase Inversion with Inputs Greater than the
Power-Supply Voltage.
FIGURE 3. Series Resistor in Unity-Gain Configuration
Improves Capacitive Load Drive.
OPA336, 2336, 4336
7
SBOS068C
www.ti.com
TI [ TEXAS INSTRUMENTS ]
