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BA1442A Dataheets PDF



Part Number BA1442A
Manufacturers Rohm
Logo Rohm
Description AM radio / FM IF stereo system IC
Datasheet BA1442A DatasheetBA1442A Datasheet (PDF)

Audio ICs AM radio / FM IF stereo system IC BA1442A The BA1442A is an AM radio and FM IF stereo system IC developed for radio cassette players. The FM circuit is comprised of a differential IF amplifier, a double-balance type quadrature detector, and a PLL-type stereo MPX circuit. The AM circuit is comprised of a local oscillator, a double-balanced mixer, an IF amplifier, a detector, and an AGC circuit. FApplications Radio cassette players FFeatures 1) The “S” curve characteristic of the FM det.

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Audio ICs AM radio / FM IF stereo system IC BA1442A The BA1442A is an AM radio and FM IF stereo system IC developed for radio cassette players. The FM circuit is comprised of a differential IF amplifier, a double-balance type quadrature detector, and a PLL-type stereo MPX circuit. The AM circuit is comprised of a local oscillator, a double-balanced mixer, an IF amplifier, a detector, and an AGC circuit. FApplications Radio cassette players FFeatures 1) The “S” curve characteristic of the FM detector can be used for upper heterodyne (“N” curve) operation. 2) Audio high cut and low cut can be used to improve the AM fidelity. 3) A reference voltage supply is provided to ensure good frequency stability in the shortwave bands. 4) Good FM stability. 5) Built-in damping resistor (3.3kΩ) for the quadrature coil. 6) The FM MPX uses a Laser Locked Loop, making adjustment of the VCO and addition of external components unnecessary. 7) Built-in forced monaural function for the MPX (VCO stops, LED off). 8) VCO of the MPX is switched off during AM operation. 9) The stereo indicator pin has a constant drive current, and a current limiting resistor is not required. 10) Few external components required. FAbsolute maximum ratings (Ta = 25_C) FRecommended operating conditions (Ta = 25_C) 337 Audio ICs FBlock diagram BA1442A FPin descriptions 338 Audio ICs BA1442A 339 Audio ICs BA1442A 340 Audio ICs BA1442A FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 5V, FM IF MPX: fin = 10.7MHz, 400Hz modulation, 22.5kHz dev (30%), 19kHz 7.5kHz dev (10%) AM: fin = 1000kHz, fm = 400Hz 30%) FMeasurement circuit 341 Audio ICs FTechnical reference materials (unless otherwise noted, Ta = 25_C and VCC = 5V) BA1442A FCircuit operation (1) The FM IF amplifier is a three-stage differential amplifier. The gain of this stage is approximately 60dB. The bias for the first-stage amplifier is taken from the bypass filter (pin 2). This improves the FM stability of the firststage amplifier by reducing noise. The input impedance is set by a resistor on the chip (330Ω), and can be connected to a ceramic filter. (2) The FM detector circuit is comprised of a quadrature detector. The IF amplified signal is input to the detector via a limiter amplifier with a gain of 13dB. (3) The AM mixer is a double-balance type, and has been designed for low local oscillator leakage. The mixer bias current is added from Vreg via antenna coil. If you lower the mixer conversion gain for mid- to high-strength electric fields, AGC will operate, and for high-strength electric fields, the input shunt AGC gives good strong-input characteristics. (4) The AM local oscillator circuit consists of a differential positive feedback loop. To improve the frequency stability, particularly in the SW band, the circuit is operated with bias referenced to Vreg. To improve the startup characteristics, a 100Ω resistor is inserted in series with the tank circuit. (5) The AM IF amplifier consis.


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