MAT02

–8–

REV. C

by various offsetting techniques. Protective diodes across each

base-to-emitter junction would normally be needed, but these

diodes are built into the MAT02. External protection diodes are

therefore not needed.

For the circuit shown in Figure 19, the operational amplifiers

output voltage for this one-quadrant, log-antilog multiplier/di-

vider is ideally:

(4)

assuming an input range of 0.1 V to +10 V.

ERROR ANALYSIS

The base-to-emitter voltage of the MAT02 in its forward active

operation is:

kT

q

In

(5)

The first term comes from the idealized intrinsic transistor

equation previously discussed (see equation (1)).

With the oscilloscope ac coupled, the temperature dependent

term becomes a dc offset and the trace represents the deviation

from true log conformity. The bulk resistance can be calculated

from the voltage deviation

∆V

rent (9 mA):

∆V

O

9 mA

×

1

100

(3)

APPLICATIONS: NONLINEAR FUNCTIONS

MULTIPLIER/DIVIDER CIRCUIT

The excellent log conformity of the MAT02 over a very wide

range of collector current makes it ideal for use in log-antilog

circuits. Such nonlinear functions as multiplying, dividing,

squaring, and square-rooting are accurately and easily imple-

mented with a log-antilog circuit using two MAT02 pairs (see

Figure 19). The transistor circuit accepts three input currents

circuit, but negative input voltages can be easily accommodated

Figure 19. One-Quadrant Multiplier/Divider