Circuit Desc:
The IC can be used with two power supply arrangements single supply and dual supply. We have decided to use the dual supply version. The single supply version would require the use of 63V electrolytic capacitors, thus increasing the cost and overall size of the module.
The input signal is coupled via R1 and C1 to the noninverting input (pin 1) of the IC. The closed loop gain of the amplifier is set to 19 by resistors R5 (180K) and R4 (10K). R4 and C3 (22uF) set the lower 3dB frequency point to 7Hz.
The output appears at pin 4 of the IC and drives a loudspeaker directly. Long speaker leads can produce enough capacitance to drive amplifiers into VHF oscillation. Resistor R6 (1W) and capacitor C4 (0.22uF) help prevent this. They are connected across the output and form a Zobel network which provides high-frequency stability when driving capacitive loads.
The IC power supply is connected via 2A fuses to protect against any external shorts to ground. Capacitors C5 and C7 provide further on-board supply decoupling.
