SA572 Philips, SA572 Datasheet - Page 7

• Manufacturer Part Number: SA572
• Description: Programmable analog compandor
• Manufacturer: Philips

Philips Semiconductors
Basic Expandor
Figure 7 shows an application of the circuit as a simple expandor.
The gain expression of the system is given by
Both the resistors R
is a 6.8k internal resistor. The maximum input current into the gain
cell can be as large as 140 A. This corresponds to a voltage level of
140 A 6.8k=952mV peak. The input peak current into the rectifier
is limited to 300 A by the internal bias system. Note that the value
of R
R
desirable system voltage and current levels. A small R
higher gain control current and smaller static and dynamic tracking
1998 Nov 03
V
V
(I
3
OUT
1
Programmable analog compandor
IN
are external resistors. It is easy to adjust the ratio of R
=140 A)
1
can be increased to accommodate higher input level. R
I
2
1
R
3
R
1
2
V
and R
IN(AVG)
R
1
2
are tied to internal summing nodes. R
Q17
Q8
I R
V IN
CA
(5)
Q9
R
10k
Figure 6. Buffer Amplifier Schematic
D11
Q10
2
results in
3
I
R1
/R
V+
2
2
for
and
D12
–
+
TRACKING
A3
TRIM
1
7
error. However, an impedance buffer A
input is voltage drive with large source impedance.
The gain cell output current feeds the summing node of the external
OPA A
voltage. In high-performance applications, A
high-speed and wide band so that the high-performance output of
the gain cell will not be degraded. The non-inverting input of A
be biased at the low noise internal reference Pin 6 or 10. Resistor
R
The output DC level of A
V
and be grounded for a single supply system. CA sets the attack time
constant and CR sets the recovery time constant. *5COL
V
B
4
ODC
is used to bias up the output DC level of A
can be tied to a regulated power supply for a dual supply system
D15
2
CR
. R
V
3
REF
and A
I
10k
R2
1
D13
2
Q14
convert the gain cell output current to the output
I
Q
R
R
=
3
4
2
2I
is given by
R2
SR00699
V
B
X2
Q18
X2
Q16
R
R
3
4
1
may be necessary if the
(6)
2
2
has to be low-noise,
for maximum swing.
Product specification
SA572
2
can