TS615IPWT(2004) View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

TS615IPWT
(Rev.:2004)

Dual Wide-Band Operational Amplifier with High Output Current

STMicroelectronics 

TS615

Choosing the Feedback Circuit

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 (910Ω).

Table 6. Closed-loop gain - feedback components

VCC (V)

±6

±2.5

Gain

+1

+2

+4

+8

-1

-2

-4

-8

+1

+2

+4

+8

-1

-2

-4

-8

Rfb (Ω)

750

680

620

510

680

680

620

510

1.1k

1k

910

680

1k

1k

910

680

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

output DC component. Assuming Ib-, Ib+, Rin, Rfb and a zero volt output, the resistance R will be:

R = Rin // Rfb

Figure 71. Compensation of the input bias current

Rfb

Ib-

Rin

_

Vcc+

TS615

+

Ib+

Vcc-

R

Output

Load

30/36

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