TLC27M7IDRG4 Datasheet, PDF (29/50 Pages) Texas Instruments – LINCMOS PRECISION DUAL OPERATIONAL AMPLIFIERS

TLC27M2, TLC27M2A, TLC27M2B, TLC27M7
LinCMOS PRECISION DUAL OPERATIONAL AMPLIFIERS
SLOS051E − OCTOBER 1987 − REVISED AUGUST 2008
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 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.
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