Op amp choice

AN4598

6/12

DocID026988 Rev 1

4

Op amp choice

The MP23AB02B microphone supply voltage is between 1.6 V and 3.6 V.

If we want to have only one power supply domain in our application, we should use a low

voltage op amp which is output rail-to-rail (especially at these low voltages where losing 1 V

really makes a difference).

Considering the noise level, slew rate, and THD requirements, the recommended

operational amplifiers are given in Table 1.

Note that all these op amps are available in automotive grade versions.

The first choice is the TS971. For driving low loads the TS922 or TS982 should be used. If

the op amp has a dedicated high-voltage power supply (single or dual supply), the

MC33078 should be used.

Table 1. Recommended op amps

Vcc

(V)

Noise

(nV/√Hz)

Slew rate

(V/µs)

Rail-to-rail

output

Minimum

load (Ω)

TS971

2.7 to 10

4

4

Yes

2 k

TS982

2.5 to 5.5

17

0.7

16

TS922

2.7 to 12

9

1.3

32

MC33078

5 to 30

4.5

7

No

600