Test Circuit
LA4450
+
100µF
IN1
100µF+
10
7
DC
VCC
9
IN1
8
NF1
+
CH1
−
BS1 6
5
OUT1
11
PRE
GND
LA4450
CH1
PWR 4
GND
CH2
PWR 3
GND
IN2
+
100µF
13
IN2
14
NF2
+
CH2
−
ST
12
BS2 1
2
OUT2
VCC=26.4V
+ 1000µF
+ 47µF
+ 1000µF
0.15µF
* RL=8Ω
2.2Ω
+ 47µF
1000µF
+
* RL=8Ω
0.15µF
2.2Ω
OFF
ON
10kΩ
+
5V
*Polyester Film Capacitor
1. Features and Usage Notes
• Pin 12 is the standby pin. The IC operates when a voltage of 2V or higher is applied through the external resistor R1.
Note that the maximum influx current to pin 12 is 500µA.
• Changing the voltage gain
The voltage gain VG can be lowered by connecting an
IN
75Ω
NF
RNf’
+
CNF
+
−
30KΩ
external resistor in series between the NF pin (pins 8 and 14)
OUT
and CNF.
30kΩ
VG = 20log 75+RNf ’
However, since the IC may oscillate if VG is 30dB or lower,
use a VG of 36dB or higher.
• The LA4450 includes a thermal protection circuit to prevent damage to or destruction of the IC due to abnormal
overheating. As a result, the output may be attenuated or cut off if the application heat sinking is inadequate.
• The LA4450 includes an overvoltage protection circuit to protect the IC against power supply surges and abnormal
voltages. This circuit has hysteresis characteristics : it operates at between 39 and 40V, and recovers at around 34V.
• Although the LA4450 includes a current limiter circuit to prevent damage due to abnormal currents, care must still be
exercised to prevent load shorts and other excessive current conditions.
No.4090-3/7