LM363 datasheet(10/22 Pages) NSC

10 / 22 page

Application Hints (Continued)

TLH5609 – 9

c Single Supply Unipolar Output

d Single Supply Bipolar Output

FIGURE 1 Reference Connections

(Continued)

OUTPUTS

The LM363’s output can typically swing within 1V of the

supplies at light loads While specified to drivea2kX load

to g10V current limit is typically 15 mA at room tempera-

ture The output can stably drive capacitive loads up to

400 pF For higher load capacitance the amplifier may be

overcompensated (see COMPENSATION section follow-

ing) The output may be continuously shorted to ground

without damaging the device

OFFSET VOLTAGE

The LM363’s offset voltage is internally trimmed to a very

low value

Note that data sheet values are given at

Tje25 C VCMe0V and Va eVbe15V For other condi-

tions warm-up drift temperature drift common-mode rejec-

tion and power supply rejection must be taken into account

Warm-up drift due to chip and package thermal gradients is

an effect separate from temperature drift Typical warm-up

drift is tabulated in the Electrical Characteristics settling

time is approximately 5 minutes in still air At load currents

up to 5 mA

thermal feedback effects are negligible

(DVOSs2mVatGe1000)

Care must be taken in measuring the extremely low offset

voltages of the high gain amplifiers Input leads must be

held isothermal to eliminate thermocouple effects Oscilla-

tions due to either heavy capacitive loading or stray capaci-

tance from input to output can cause erroneous readings

In either case overcompensation will help High frequency

noise fed into the inputs may be rectified internally and pro-

duce an offset shift A simple low-pass RC filter will usually

cure this problem (

Figure 2 ) Use film type resistors for their

low thermal EMF In highly noisy environments LC filters

can be substituted for increased RF attenuation

TLH5609 – 10

FIGURE 2 Low Pass Filter Prevents RF Rectification

Instrumentation amplifiers have both an input offset voltage

(VIOS) and an output offset voltage (VOOS) The total input-

referred offset voltage (VOSRTI) is related to the instrumen-

tation amplifier gain (G) as follows VOSRTIeVIOSaVOOS

G The offset voltage given in the LM363 specifications is

the total input-referred offset As long as only one gain is

used offset voltage can be nulled at either input or output

as shown in

Figures 3a and 3b When the 16-pin device is

used at multiple gain settings both VIOS and VOOS should

be nulled to get minimum offset at all gains as shown in

Figure 3c The correct procedure is to trim VOOS for zero

output at Ge10 then trim VIOS at Ge1000

TLH5609 – 11

FIGURE 3 Offset Voltage Trimming

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