TLC27M2 Datasheet, PDF (29/34 Pages) Texas Instruments – LinCMOSE PRECISION DUAL OPERATIONAL AMPLIFIERS

TLC27M2, TLC27M2A, TLC27M2B, TLC27M7
LinCMOS™ PRECISION DUAL OPERATIONAL AMPLIFIERS
SLOS051C – OCTOBER 1987 – REVISED MAY 1999
APPLICATION INFORMATION
(a) CL = 20 pF, RL = NO LOAD
(b) CL = 170 pF, RL = NO LOAD
2.5 V
VO
VI
TA = 25°C
CL f = 1 kHz
VI(PP) = 1 V
– 2.5 V
(c) CL = 190 pF, RL = NO LOAD
(d) TEST CIRCUIT
Figure 41. Effect of Capacitive Loads and Test Circuit
output characteristics (continued)
Although the TLC27M2 and TLC27M7 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 op amp 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.
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