參數(shù)資料
型號: TLC274MFK
廠商: Texas Instruments, Inc.
英文描述: LinCMOSE PRECISION QUAD OPERATIONAL AMPLIFIERS
中文描述: LinCMOSE精密四運算放大器
文件頁數(shù): 31/42頁
文件大?。?/td> 668K
代理商: TLC274MFK
TLC274, TLC274A, TLC274B, TLC274Y, TLC279
LinCMOS
PRECISION QUAD OPERATIONAL AMPLIFIERS
SLOS092C – SEPTEMBER 1987 – REVISED MARCH 1998
31
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
APPLICATION INFORMATION
input characteristics
The TLC274 and TLC279 are 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. Note that the lower range limit includes the negative rail, while the upper range limit
is specified at V
DD
– 1 V at T
A
= 25
°
C and at V
DD
– 1.5 V at all other temperatures.
The use of the polysilicon-gate process and the careful input circuit design gives the TLC274 and TLC279 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
μ
V/month, including the first month of
operation.
Because of the extremely high input impedance and resulting low bias current requirements, the TLC274 and
TLC279 are 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 4 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 40).
Unused amplifiers should be connected as grounded unity-gain followers to avoid possible oscillation.
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 TLC274 and TLC279 result in a very low
noise current, which is insignificant in most applications. This feature makes the devices especially favorable
over bipolar devices when using values of circuit impedance greater than 50 k
, since bipolar devices exhibit
greater noise currents.
VI
(a) NONINVERTING AMPLIFIER
(c) UNITY-GAIN AMPLIFIER
+
(b) INVERTING AMPLIFIER
VI
+
+
VI
VO
VO
VO
Figure 40. Guard-Ring Schemes
output characteristics
The output stage of the TLC274 and TLC279 is designed to sink and source relatively high amounts of current
(see typical characteristics). If the output is subjected to a short-circuit condition, this high current capability can
cause device damage under certain conditions. Output current capability increases with supply voltage.
All operating characteristics of the TLC274 and TLC279 were measured using a 20-pF load. The devices drive
higher capacitive loads; however, as output load capacitance increases, the resulting response pole occurs at
lower frequencies, thereby causing ringing, peaking, or even oscillation (see Figure 41). In many cases, adding
a small amount of resistance in series with the load capacitance alleviates the problem.
相關(guān)PDF資料
PDF描述
TLC274Y LinCMOSE PRECISION QUAD OPERATIONAL AMPLIFIERS
TLC279MD LinCMOSE PRECISION QUAD OPERATIONAL AMPLIFIERS
TLC279MFK LinCMOSE PRECISION QUAD OPERATIONAL AMPLIFIERS
TLC279MJ LinCMOSE PRECISION QUAD OPERATIONAL AMPLIFIERS
TLC279MN LinCMOSE PRECISION QUAD OPERATIONAL AMPLIFIERS
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