Datasheet

TLC4501, TLC4501A, TLC4502, TLC4502A
FAMILY OF SELF-CALIBRATING (Self-Cal)
PRECISION CMOS RAIL-TO-RAIL OUTPUT OPERATIONAL AMPLIFIERS
SLOS221B – MAY 1998 – REVISED APRIL 2001
20
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
The TLC4502 is designed to operate with only a single 5-V power supply, have true differential inputs, and
remain in the linear mode with an input common-mode voltage of 0.
The TLC4502 has a standard dual-amplifier pinout, allowing for easy design upgrades.
Large differential input voltages can be easily accommodated and, as input differential-voltage protection
diodes are not needed, no large input currents result from large differential input voltage. Protection should
be provided to prevent the input voltages from going negative more than –0.3 V at 25°C. An input clamp
diode with a resistor to the device input terminal can be used for this purpose.
For ac applications, where the load is capacitively coupled to the output of the amplifier, a resistor can be
used from the output of the amplifier to ground. This increases the class-A bias current and prevents
crossover distortion. Where the load is directly coupled, for example in dc applications, there is no crossover
distortion.
Capacitive loads, which are applied directly to the output of the amplifier, reduce the loop stability margin.
Values of 500 pF can be accommodated using the worst-case noninverting unity-gain connection. Resistive
isolation should be considered when larger load capacitance must be driven by the amplifier.
The following typical application circuits emphasize operation on only a single power supply. When
complementary power supplies are available, the TLC4502 can be used in all of the standard operational
amplifier circuits. In general, introducing a pseudo-ground (a bias voltage of V
I
/2 like that generated by the
TLE2426) allows operation above and below this value in a single-supply system. Many application circuits
shown take advantage of the wide common-mode input-voltage range of the TLC4502, which includes ground.
In most cases, input biasing is not required and input voltages that range to ground can easily be
accommodated.
description of calibration procedure
To achieve high dc gain, large bandwidth, high CMRR and PSRR, as well as good output drive capability, the
TLC4502 is built around a 3-stage topology: two gain stages, one rail-to-rail, and a class-AB output stage. A
nested Miller topology is used for frequency compensation.
During the calibration procedure, the operational amplifier is removed from the signal path and both inputs are
tied to GND. Figure 35 shows a block diagram of the amplifier during calibration mode.