TLV2322, TLV2322Y, TLV2324, TLV2324Y

LinCMOS

™ LOW-VOLTAGE LOW-POWER

OPERATIONAL AMPLIFIERS

SLOS187 – FEBRUARY 1997

25

POST OFFICE BOX 655303

APPLICATION INFORMATION

single-supply operation (continued)

The TLV232x works well in conjunction with digital logic; however, when powering both linear devices and digital

logic from the same power supply, the following precautions are recommended:

device supply rails can fluctuate due to voltage drops caused by high switching currents in the digital

logic.

decoupling is often adequate; however, RC decoupling may be necessary in high-frequency

applications.

–

+

Logic

Logic

Logic

Power

Supply

–

+

Logic

Logic

Logic

Power

Supply

(a) COMMON-SUPPLY RAILS

(b) SEPARATE-BYPASSED SUPPLY RAILS (preferred)

Figure 41. Common Versus Separate Supply Rails

input characteristics

The TLV232x is specified with a minimum and a maximum input voltage that, if exceeded at either input, could

cause the device to malfunction. Exceeding this specified range is a common problem, especially in

single-supply operation. The lower the range limit includes the negative rail, while the upper range limit is

The use of the polysilicon-gate process and the careful input circuit design gives the TLV232x very good input

offset voltage drift characteristics relative to conventional metal-gate processes. Offset voltage drift in CMOS

devices is highly influenced by threshold voltage shifts caused by polarization of the phosphorus dopant

implanted in the oxide. Placing the phosphorus dopant in a conductor (such as a polysilicon gate) alleviates the

polarization problem, thus reducing threshold voltage shifts by more than an order of magnitude. The offset

voltage drift with time has been calculated to be typically 0.1

µV/month, including the first month of operation.

Because of the extremely high input impedance and resulting low bias-current requirements, the TLV232x is

well suited for low-level signal processing; however, leakage currents on printed-circuit boards and sockets can

easily exceed bias-current requirements and cause a degradation in device performance. 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.