Datasheet

   
    
SLOS051E − OCTOBER 1987 − REVISED AUGUST 2008
27
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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
V
O
V
DD
R2
R1
V
I
V
REF
R3
C
0.01µF
−
+
V
REF
+ V
DD
R3
R1 ) R3
V
O
+
ǒ
V
REF
–V
I
Ǔ
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