CXB1577Q
Notes on Operation
1. Limiting amplifier block
The limiting amplifier block is equipped with the auto-offset canceler circuit. When external capacitors C1 and
C2 are connected as shown in Fig. 1, the DC bias is set automatically in this block. External capacitor C1 and
IC internal resistor R1 determine the low input cut-off frequency f2 as shown in Fig. 2. Similarly, external
capacitor C2 and IC internal resistor R2 determine the high cut-off frequency f1 for DC bias feedback. Since
peaking characteristics may occur in the low frequency area of the amplifier gain characteristics depending on
the f1/f2 combination, set the C1 and C2 values so as to avoid the occurrence of peaking characteristics. The
target values of R1 and R2 and the typical values of C1 and C2 are as indicated below. When a single-ended
input is used, provide AC grounding by connecting Pin 17 to a capacitor which has the same capacitance as
capacitor C1.
R1 (internal): 1kΩ
C1 (external): 0.047µF
f2: 3.4kHz
R2 (internal): 7.5kΩ
C2 (external): 1µF
f1: 21Hz
D
18
C1
17
C1
16
C2
15
R1
R1
R2
R2
Fig. 1
To IC interior
Feedback frequency
response
Amplifier frequency
response
f1 f2
Frequency
Fig. 2
– 13 –