TLC272BCDR Datasheet, PDF (31/51 Pages) Texas Instruments – LinCMOS PRECISION DUAL OPERATIONAL AMPLIFIERS

TLC272, TLC272A, TLC272B, TLC272Y, TLC277
LinCMOS PRECISION DUAL OPERATIONAL AMPLIFIERS
SLOS091E – OCTOBER 1987 – REVISED FEBRUARY 2002
APPLICATION INFORMATION
output characteristics (continued)
(a) CL = 20 pF, RL = NO LOAD
(b) CL = 130 pF, RL = NO LOAD
2.5 V
VI
VO
CL
TA = 25°C
f = 1 kHz
VIPP = 1 V
– 2.5 V
(c) CL = 150 pF, RL = NO LOAD
(d) TEST CIRCUIT
Figure 41. Effect of Capacitive Loads and Test Circuit
Although the TLC272 and TLC277 possess excellent high-level output voltage and current capability, methods
for boosting this capability are available, if needed. The simplest method involves the use of a pullup resistor
(R_P) connected from the output to the positive supply rail (see Figure 42). There are two disadvantages to the
use of this circuit. First, the NMOS pulldown transistor N4 (see equivalent schematic) must sink a comparatively
large amount of current. In this circuit, N4 behaves like a linear resistor with an on resistance between
approximately 60 Ω and 180 Ω, depending on how hard the operational amplifier input is driven. With very low
values of R_P, a voltage offset from 0 V at the output occurs. Second, pullup resistor R_P acts as a drain load to
N4 and the gain of the operational amplifier is reduced at output voltage levels where N5 is not supplying the
output current.
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
31