MPY634AM datasheet(5/19 Pages) TI2

5 / 19 page

MPY634

SBFS017A

www.ti.com

TYPICAL PERFORMANCE CURVES (CONT)

A = +25°C, VS = ±15VDC, unless otherwise noted.

THEORY OF OPERATION

The transfer function for the MPY634 is:

VOUT = A

– (Z1 – Z2)

where:

A = open-loop gain of the output amplifier (typically

85dB at DC).

SF = Scale Factor. Laser-trimmed to 10V but adjustable

over a 3V to 10V range using external resistors.

X, Y, Z are input voltages. Full-scale input voltage

is equal to the selected SF. (Max input voltage =

±1.25 SF).

An intuitive understanding of transfer function can be gained

by analogy to the op amp. By assuming that the open-loop

gain, A, of the output operational amplifier is infinite,

1 – X2) (Y1 – Y2)

inspection of the transfer function reveals that any VOUT can

be created with an infinitesimally small quantity within the

brackets. Then, an application circuit can be analyzed by

assigning circuit voltages for all X, Y and Z inputs and

setting the bracketed quantity equal to zero. For example,

the basic multiplier connection in Figure 1, Z1 = VOUT and

Z2 = 0. The quantity within the brackets then reduces to:

– (VOUT – 0) = 0

This approach leads to a simple relationship which can be

solved for VOUT to provide the closed-loop transfer function.

The scale factor is accurately factory adjusted to 10V and is

typically accurate to within 0.1% or less. The scale factor

may be adjusted by connecting a resistor or potentiometer

between pin SF and the –VS power supply. The value of the

external resistor can be approximated by:

1 – X2) (Y1 – Y2)

810

Positive or Negative Supply (V)

INPUT/OUTPUT SIGNAL RANGE

vs SUPPLY VOLTAGES

Output, R

L ≥ 2kΩ

All inputs, SF = 10V

–10

INPUT DIFFERENTIAL-MODE/

COMMON-MODE VOLTAGE

–12

–5

–55

–10

Specified

Accuracy

S = ±15V

Functional

Derated Accuracy

DIFF

800

700

600

500

400

300

200

100

–20

100

140

Temperature (°C)

BIAS CURRENTS vs TEMPERATURE

(X,Y or Z Inputs)

–40

120

Scaling Voltage = 10V

Scaling Voltage = 3V

–60

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