TLC27M4, TLC27M4A, TLC27M4B, TLC27M4Y, TLC27M9

LinCMOS

™ PRECISION QUAD OPERATIONAL AMPLIFIERS

SLOS093C – OCTOBER 1987 – REVISED MAY 1999

19

POST OFFICE BOX 655303

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 < BOM

(c) f = BOM

(d) f > BOM

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.