TLC27L1_08 Datasheet, PDF (21/32 Pages) Texas Instruments – LinCMOSE LOW-POWER OPERATIONAL AMPLIFIERS

TLC27L1, TLC27L1A, TLC27L1B
LinCMOS LOWĆPOWER
OPERATIONAL AMPLIFIERS
SLOS154B− DECEMBER 1995 − REVISED JUNE 2005
PARAMETER MEASUREMENT INFORMATION
8
5
V = VIC
1
4
Figure 36. Isolation Metal Around Device Inputs (JG and P packages)
low-level output voltage
To obtain low-supply-voltage operation, some compromise is necessary in the input stage. This compromise
results in the device low-level output being dependent on both the common-mode input voltage level as well
as the differential input voltage level. When attempting to correlate low-level output readings with those quoted
in the electrical specifications, these two conditions should be observed. When conditions other than these are
to be used, please refer to the Typical Characteristics section of this data sheet.
input offset-voltage temperature coefficient
Erroneous readings often result from attempts to measure the temperature coefficient of input offset voltage.
This parameter is actually a calculation using input offset-voltage measurements obtained at two different
temperatures. When one (or both) of the temperatures is below freezing, moisture can collect on both the device
and the test socket. This moisture results in leakage and contact resistance which can cause erroneous input
offset-voltage readings. The isolation techniques previously mentioned have no effect on the leakage since the
moisture also covers the isolation metal itself, thereby rendering it useless. It is suggested that these
measurements be performed at temperatures above freezing to minimize error.
full-power response
Full-power response, the frequency above which the amplifier slew rate limits the output voltage swing, is often
specified two ways: full-linear response and full-peak response. The full-linear response is generally measured
by monitoring the distortion level of the output while increasing the frequency of a sinusoidal input signal until
the maximum frequency is found above which the output contains significant distortion. The full-peak response
is defined as the maximum output frequency, without regard to distortion, above which full peak-to-peak output
swing cannot be maintained.
Since there is no industry-wide accepted value for significant distortion, the full-peak response is specified in
this data sheet and is measured using the circuit in Figure 33. The initial setup involves the use of a sinusoidal
input to determine the maximum peak-to-peak output of the device (the amplitude of the sinusoidal wave is
increased until clipping occurs). The sinusoidal wave is then replaced with a square wave of the same
amplitude. The frequency is then increased until the maximum peak-to-peak output can no longer be maintained
(Figure 37). A square wave allows a more accurate determination of the point at which the maximum
peak-to-peak output is reached.
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