Equivalent Circuit Block Diagram
AC Test Circuit
T1: CBTKAC-24782 AUO (Toko Co.)
T2: CBTKAE-24783X (Toko Co.)
22µH: S-220J (Korin Co.)
Input signal strength is an actual input at pin 1
The muting operation in the LA1140 is performed by an AF preamplifier, the gain of which varies continuously with control
current, and a muting drive output circuit which supplies the control current.
The gain of the AF preamplifier decreases with increasing gain control current applied to pin 6. However, the gain does not
decrease further when the control current reaches approximately 120 µA or greater. The lower limit of the gain under this
condition depends upon a Resistor connected between pin 5 and GND, and the higher the resistance the lower the gain (the higher the attenuation). Thus the maximum muting attenuation will be set by connecting the Resistor between pin 5 and GND.
R5-G (lower) 20 kΩ
R5-G (higher) 100 kΩ