–12–

SMP04

REV. D

SAMPLE AND DIFFERENCE AMPLIFIER (Figure 23)

This circuit uses two sample-and-holds to measure the voltage

sampled voltages are fed into the differential inputs of the AMP02

this instrumentation amplifier. Using two channels of the

SMP04 in this application has the advantage of matched

sample-and-hold performance, since they are both on the same

chip.

DGND

+12V

1/2 SMP04

AMP02

+12V

–5V OR –12V

G =

+1

50k

S/H (DELAYED)

S/H

0

0

INSTRUMENTATION AMP

Figure 23. Time Delta Sample-and-Difference Measurement

SINGLE SUPPLY, SAMPLING, INSTRUMENTATION

AMPLIFIER (Figure 24)

This application again uses two channels of the SMP04 and an

instrumentation amplifier to provide a sampled difference signal.

The sample-and-hold signals in this circuit are tied together to

sample at the same point in time. The other two parts of the

SMP04 are used as amplifiers by grounding their control lines

so they are always sampling. One section is used to drive a

guard to the common-mode voltage and the other to generate a

+6 V reference to serve as an offset for single supply operation.

+6V REFERENCE

REFERENCE

AMP02

1/4

SMP04

1/4

SMP04

1/4

SMP04

1/4

SMP04

0.1 F

GAIN =

50k

+1

50k

50k

+12V

20k

20k

0.01 F

GUARD

GUARD

GUARD

DRIVE

S/H

+ INPUT

– INPUT

+12V

+12V

Figure 24. +12 V Single Supply Sampling Instrumentation Amplifier with Guard Drive