TLC27M4, TLC27M4A, TLC27M4B, TLC27M4Y, TLC27M9
LinCMOS PRECISION QUAD OPERATIONAL AMPLIFIERS
SLOS093C – OCTOBER 1987 – REVISED MAY 1999
19
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PARAMETER MEASUREMENT INFORMATION
input offset voltage temperature coefficient
Erroneous readings often result from attempts to measure 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 operational 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.
Because 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 of Figure 1. 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 5). A square wave is used to allow a more accurate determination of the point at which the maximum
peak-to-peak output is reached.
(a) f = 1 kHz (b) 1 kHz < f < B
OM
(c) f = B
OM
(d) f > B
OM
Figure 5. Full-Power-Response Output Signal
test time
Inadequate test time is a frequent problem, especially when testing CMOS devices in a high-volume,
short-test-time environment. Internal capacitances are inherently higher in CMOS than in bipolar and BiFET
devices and require longer test times than their bipolar and BiFET counterparts. The problem becomes more
pronounced with reduced supply levels and lower temperatures.
