TLC27M2, TLC27M2A, TLC27M2B, TLC27M7

LinCMOS

™ PRECISION DUAL OPERATIONAL AMPLIFIERS

SLOS051C – OCTOBER 1987 – REVISED MAY 1999

27

POST OFFICE BOX 655303

APPLICATION INFORMATION

single-supply operation

While the TLC27M2 and TLC27M7 perform well using dual power supplies (also called balanced or split

supplies), the design is optimized for single-supply operation. This design includes an input common-mode

voltage range that encompasses ground as well as an output voltage range that pulls down to ground. The

supply voltage range extends down to 3 V (C-suffix types), thus allowing operation with supply levels commonly

available for TTL and HCMOS; however, for maximum dynamic range, 16-V single-supply operation is

recommended.

Many single-supply applications require that a voltage be applied to one input to establish a reference level that

is above ground. A resistive voltage divider is usually sufficient to establish this reference level (see Figure 38).

The low input bias current of the TLC27M2 and TLC27M7 permits the use of very large resistive values to

implement the voltage divider, thus minimizing power consumption.

The TLC27M2 and TLC27M7 work 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:

1.

Power the linear devices from separate bypassed supply lines (see Figure 39); otherwise, the linear

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

logic.

2.

Use proper bypass techniques to reduce the probability of noise-induced errors. Single capacitive

decoupling is often adequate; however, high-frequency applications may require RC decoupling.

R4

VO

VDD

R2

R1

VI

VREF

R3

C

0.01

µF

V

REF

+ V

DD

R3

R1

) R3

V

O

+

V

REF

–V

I

R4

R2

) V

REF

Figure 38. Inverting Amplifier With Voltage Reference

(a) COMMON SUPPLY RAILS

Logic

Power

Supply

Logic

Logic

Logic

Logic

Logic

(b) SEPARATE BYPASSED SUPPLY RAILS (preferred)

Power

Supply

Output

Output

Figure 39. Common Versus Separate Supply Rails