–

+

Figure 43. Compensation for Input Capacitance

TLV2342, TLV2342Y, TLV2344, TLV2344Y

LinCMOS

™ LOW-VOLTAGE HIGH-SPEED

OPERATIONAL AMPLIFIERS

SLOS194 – FEBRUARY 1997

27

POST OFFICE BOX 655303

APPLICATION INFORMATION

input characteristics (continued)

It is good practice to include guard rings around inputs (similar to those of Figure 38 in the Parameter

Measurement Information section). These guards should be driven from a low-impedance source at the same

voltage level as the common-mode input (see Figure 42).

The inputs of any unused amplifiers should be tied to ground to avoid possible oscillation.

–

+

–

+

–

+

(a) NONINVERTING AMPLIFIER

(b) INVERTING AMPLIFIER

(c) UNITY-GAIN AMPLIFIER

VO

VI

VO

VO

Vi

VI

Figure 42. Guard-Ring Schemes

noise performance

The noise specifications in operational amplifier circuits are greatly dependent on the current in the first-stage

differential amplifier. The low input bias-current requirements of the TLV234x results in a very low noise current,

which is insignificant in most applications. This feature makes the device especially favorable over bipolar

devices when using values of circuit impedance greater than 50 k

Ω, since bipolar devices exhibit greater noise

currents.

feedback

Operational amplifiers circuits nearly always

employ feedback, and since feedback is the first

prerequisite for oscillation, a little caution is

appropriate. Most oscillation problems result from

driving capacitive loads and ignoring stray input

capacitance. A small-value capacitor connected

in parallel with the feedback resistor is an effective

remedy (see Figure 43). The value of this

capacitor is optimized empirically.

electrostatic-discharge protection

The TLV234x incorporates an internal electrostatic-discharge (ESD)-protection circuit that prevents functional

failures at voltages up to 2000 V as tested under MIL-PRF-38535. Method 3015.2. Care should be exercised,

however, when handling these devices as exposure to ESD may result in the degradation of the device

parametric performance. The protection circuit also causes the input bias currents to be temperature dependent

and have the characteristics of a reverse-biased diode.