5–8

IL300

These amplifiers provide either an inverting or non-inverting

transfer gain based upon the type of input and output amplifier.

Table 2 shows the various configurations along with the spe-

cific transfer gain equations. The offset column refers to the

calculation of the output offset or Vref2 necessary to provide a

zero voltage output for a zero voltage input. The non-inverting

input amplifier requires the use of a bipolar supply, while the

inverting input stage can be implemented with single supply

operational amplifiers that permit operation close to ground.

For best results, place a buffer transistor between the LED and

output of the operational amplifier when a CMOS opamp is

Finally the bandwidth is influenced by the magnitude of the

closed loop gain of the input and output amplifiers. Best band-

widths result when the amplifier gain is designed for unity.

Figure 22. Non-inverting and inverting amplifiers

Table 2. Optolinear amplifiers

Amp[ifier

Input

Output

Gain

Offset

Non-Inverting

Inverting

Inverting

Non-Inverting

Non-Inverting

Inverting

Inverting

Non-Inverting

Non-Inverting

Inverting

Vcc

20pF

4

1

2

3

4

8

7

6

5

+Vref2

R5

R6

7

2

4

3

Vo

R4

R3

–Vref1

Vin

R1

R2

3

7

6

+

+Vcc

100

Ω

6

IL 300

2

–Vcc

–Vcc

Vcc

–Vcc

+

Vcc

Vcc

20pF

4

1

2

3

4

8

7

6

5

+Vref2

7

2

4

3

Vout

R4

R3

+Vref1

Vin

R1

R2

3

7

6

+

+Vcc

100

Ω

6

2

Vcc

Vcc

–Vcc

+

Vcc

–

–

Non-Inverting Input

Non-Inverting Output

Inverting Input

Inverting Output

IL 300

–

–

–Vcc

R3 (R1+R2)

=

R3

R3 R5 (R1 +R2)

=

R3 R6

R3 R5 (R1 +R2)

=

R3 R6

R3 (R1 +R2)

=

R3