MAT02

–10–

REV. C

Collector-current range is the key design decision. The inher-

collector current. For input scaling of

±10 V full-scale and us-

–10

+

10









≤ I

10

+

10









(13)

100 k

Ω. Choosing an R

Ω and R

Ω provides a

collector-current range of approximately 39

µA to 283 µA. An

for

±10 V full scale.

Linear error for this circuit is substantially improved by the

small correction voltage applied to the base of Q1 as shown in

Figure 21. Assuming an equal bulk emitter resistance for each

MAT02 transistor, then the error is nulled if:

ρV

The currents are known from the previous discussion, and the

relationship needed is simply:

(14)

plied to the base of Q1 to cancel the summation of voltage

rate relationship. Linearity of better than 0.1% is readily achiev-

able with this circuit if the MAT02 pairs are carefully kept at

the same temperature.

MULTIFUNCTION CONVERTER

The multifunction converter circuit provides an accurate means

of squaring, square rooting, and of raising ratios to arbitrary

powers. The excellent log conformity of the MAT02 allows a

wide range of exponents. The general transfer function is:









m

(15)

often taken from a fixed reference voltage. With a REF01 pro-

tion would simplify to:

10









m

(16)

As with the multiplier/divider circuits, assume that the transistor

pairs have excellent matching and are at the same temperature.

voltage drops across the base-emitter junctions of Q1 provide:

kT

q

In

(17)

A

kT

q

In

I

Y

(18)

then be combined.

A

In

= In

(19)

Figure 21. Four-Quadrant Multiplier