TL441EP

LOGARITHMIC AMPLIFIER

SGLS268 − OCTOBER 2004

9

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

Output Levels

Differential-output-voltage levels are low, generally less than 0.6 V. As demonstrated in Figure 11, the output

swing and the slope of the output response can be adjusted by varying the gain by means of the slope control.

The coordinate origin also can be adjusted by positioning the offset of the output buffer.

Circuits

Figure 11 through Figure 18 show typical circuits using this logarithmic amplifier. Operational amplifiers not

otherwise designated are TLC271. For operation at higher frequencies, the TL592 is recommended instead of

the TLC271.

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

− 0.2

10 − 4

10 −3

10 −2

10 −1

101

1

TYPICAL TRANSFER CHARACTERISTICS

Adjusted for Increased

Slope and Offset

Adjusted For Minimum

Slope With Zero Offset

Input Voltage − V

Input

A1

A2

Y

Y

1/2

TL441

Origin

Slope

Output

GND

+

−

+

−

Figure 11. Output Slope and Origin Adjustment