TS615

Choosing the Feedback Circuit

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10 Choosing the Feedback Circuit

As described on Figure 72 on page 31, the TS615 requires a 620

Ω feedback resistor to optimize the

bandwidth with a gain of 12 dB for a 12 V power supply. Nevertheless, due to production test constraints,

the TS615 is tested with the same feedback resistor for 12 V and 5 V power supplies (910

Ω).

10.1 The bias of an inverting amplifier

A resistance is necessary to achieve a good input biasing, such as resistance R, shown in Figure 71.

The magnitude of this resistance is calculated by assuming the negative and positive input bias current.

The aim is to compensate for the offset bias current, which could affect the input offset voltage and the

Table 6. Closed-loop gain - feedback components

Gain

±6

+1

750

+2

680

+4

620

+8

510

-1

680

-2

680

-4

620

-8

510

±2.5

+1

1.1k

+2

1k

+4

910

+8

680

-1

1k

-2

1k

-4

910

-8

680

Figure 71. Compensation of the input bias current

R

Load

Output

Ib-

Ib+

Vcc+

Vcc-

TS615

+

_

R

Load

Output

Ib-

Ib+

Vcc+

Vcc-

TS615

+

_