Datasheet
SLOS052D − OCTOBER 1987 − REVISED OCTOBER 2005
28
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
output characteristics (continued)
(b) C
L
= 260 pF, R
L
= NO LOAD(a) C
L
= 20 pF, R
L
= NO LOAD
V
I
−2.5 V
C
L
V
O
2.5 V
−
+
T
A
= 25°C
f = 1 kHz
V
I(PP)
= 1 V
(d) TEST CIRCUIT
(c) C
L
= 310 pF, R
L
= NO LOAD
Figure 41. Effect of Capacitive Loads and Test Circuit
Although the TLC27L2 and TLC27L7 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.