ASAHI KASEI

[AKD4626A-B]

<KM079800>

2005/11

- 6 -

Consideration for analog output circuit

AK4626A

22u

Signal

6.0Vpp

28

27

26

25

ROUT1

Same circuit

3.0Vpp

NJM4580

+

-

LOUT1

ROUT2

LOUT2

ROUT3

LOUT3

24

23

Same circuit

Same circuit

Same circuit

Same circuit

10k

4.7k

4.7k

330p

220

1) Frequency response of HPF

The HPF is implemented on board to cancel the DC offset of analog output of AK4626A.

Frequency response of 1st-order HPF

| Amplitude |

πRC=0.7Hz@R=10k,C=22u

fin

20Hz

Frequency Response

-0.006dB

2) Gain, S/N and frequency response of op-amp circuit

1st-order filter with non-inverting amp is implemented on board to double the analog output level and attenuate out-of-band

noise.

a) Gain

The gain is

1+4.7k/4.7k = +6.02dB.

Therefore the output level of this board is

0.51dBV(=3.0Vpp) + 6.02dB

= 6.53dBV = 6.00Vpp = 2.12Vrms.

b) S/N (Theory: BW=20k+A)

The output noise level of non-inverting amp

-110.36dBV = -116.89dB (0dB=6.53dBV)

S/N of DAC is

106.3dB (measurement)

Therefore total S/N of op-amp circuit and DAC is

105.94dB (measurement: 106.1dB).