JBL LSR28P, Техническое и сервисное руководство

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HIGH FREQUENCY AMPLIFIER
The circuit shown above is the high frequency power amplifier used in the LSR28P. It uses
an LM3886T operational power amplifier in a non-inverting configuration with the normal
peripheral components to provide proper equalization and operation. The nominal operating
voltage of positive and negative 36V is applied to the IC via pin 4 and pins 1 and 5, respectively.
Further power supply filtering is performed by C#^ and C28. The negative feedback resistor,
R36, in conjunction with R53 determine the amplifier’s closed-loop gain according to the
equation:
GAIN = 1/B where B = attenuation of feedback network
= R53/(R53 + R36) = .06976
= 1/. 06976 = 14.33 = 14.3
Signal input from the previous printed circuit board is capacitively coupled by C25 and
serially reduced by R52 and connected to the inverting input of the IC. Operating stability is
added when the inverting input is referenced to ground through the shunt of R53 and C34. C35 is
shunted across the inverting and non-inverting inputs utilizing the properties of common mode
rejection, thereby eliminating any ultra -high frequency noise through signal cancellation. Offset
voltage is detected at the output of the IC at pin 3, which connects to the detection/mute circuits
via R49. The polarity of an abnormal DC voltage is determined by the detection circuitry and is
processed accordingly.
Input = . 8Vpp @ 10KHz
Output = 11.8 Vpp