BA3306

Audio ICs Dual preamplifier with ALC BA3306 The BA3306 is a dual preamplifier with ALC designed for use in stereo radio-cassette recorders and tape recorders. It comes in a compact 9-pin SIP package and has two record / playback preamplifiers, and an ALC circuit. The preamplifiers have high gain and low distortion, and can be directly coupled to the tape head without coupling capacitors. This prevents tape head magnetization and “pop” noise generation. The ALC circuit has good channel balance and large dynamic range and can be constructed with addition of just an external detector and time constant circuit. The IC also includes a power-on mute circuit that suppresses “pop” noise generation. FApplications Stereo radio cassette players FFeatures 1) Wide operating power supply voltage range (VCC = 4.5V to 14V). 2) Low current dissipation (IQ = 2.5mA). 3) High gain (GVO = 80dB). 4) Low distortion (THD = 0.1%). FBlock diagram 5) 6) 7) 8) Low noise (VNIN = 1µVrms). Input coupling capacitors and not necessary. Good ALC channel balance. Power-on mute circuit. FAbsolute maximum ratings (Ta = 25_C) 201 Audio ICs FRecommended operating conditions (Ta = 25_C) BA3306 FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 7V, and f= 1kHz) FMeasurement circuit 202 Audio ICs FApplication example BA3306 FCircuit operation (1) Recording (See Fig. 3) For recording, insert an attenuation resistor (3.9kΩ recommended) into the input line. The ALC timing is determined by the time constant of the circuit connected between pin 5 and GND. The attack time is set the capacitor (22µF) and the resistor (4.7kΩ) that is connected in series with the diode. The recovery time is set by this capacitor and the resistor (1MΩ) connected to pin 5. (2) Playback (See Fig. 4) For playback, the amplifier is used as a NAB equalizer amplifier. The ALC circuit is not needed at this time, so pin 5 is earthed. The negative feedback time constant settings are Hi - 120µs and Lo - 3180µs. 203 Audio ICs FElectrical characteristics curves BA3306 204 Audio ICs FExternal dimensions (Units: mm) BA3306 205