BA3308 / BA3308F Audio ICs Dual preamplifier with ALC BA3308 / BA3308F The BA3308 and BA3308F are dual preamplifier ICs with built-in ALC circuits, and have been designed for use in stereo radio-cassette recorders and tape recorders. They come in compact 9-pin SIP (BA3308) and 14-pin MF (BA3308F) packages, and have 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. A built-in rectifier means that an ALC circuit with good channel balance and large dynamic range can be constructed with addition of just an external time constant circuit. The ICs also include power-on mute circuits that suppress "pop" noise generation. !Applications Stereo radio cassette recorders, cassette decks and home stereo systems and music centers !Features 1) Built-in ALC rectifier diode. 2) Wide operating power supply voltage range (VCC=6.0V to 14V) 3) Low current dissipation (IQ=3.5mV) 4) High gain (GVO=80dB) 5) Low distortion (THD=0.1%) 6) Low noise (VNIN=1Vrms) 7) Input coupling capacitors and not necessary. 8) Good ALC channel balance. 9) Power-on mute circuit. 10) ALC dynamic range can be varied by the addition of an external input resistor. !Absolute maximum ratings (Ta=25C) Parameter Power supply voltage BA3308 Power dissipation BA3308F Symbol Limits Unit VCC 16 V Pd 950 1 450 2 mW Operating temperature Topr -25 to +75 C Storage temperature Tstg -55 to +125 C 1 Reduced by 9.5mW for each increase in Ta of 1C over 25C. 2 Reduced by 4.5mW for each increase in Ta of 1C over 25C (when mounted on a 70mm x 70mm x 1.6mm glass epoxy board). !Recommended operating conditions (Ta=25C) Parameter Power supply voltage Symbol Min. Typ. Max. Unit VCC 6.0 - 14 V 1/8 BA3308 / BA3308F Audio ICs !Block diagram BA3308 MUTE - - ch2 ch1 + + 6 7 VCC OUTPUT2 8 9 NF2 5 INPUT2 4 ALC INPUT1 3 GND 2 OUTPUT1 1 NF1 ALC BA3308F 14 N.C. 1 + - 2 N.C. 3 ALC 4 5 13 12 N.C. 11 - + Vcc N.C. 6 10 9 8 N.C. 7 !Electrical characteristics (unless otherwise noted, Ta=25C, VCC=7.0V, f=1kHz and BPF: 20Hz20kHz) Parameter Symbol Min. Typ. Max. Unit IQ 1.5 3.5 4.5 mA VIN=0Vrms Open loop voltage gain GVO 70 80 - dB VOUT=-10dBV Total harmonic distortion THD - 0.1 0.3 % NAB34dB, VOUT=40mVrms Quiescent current Conditions - Input resistance RIN 15 25 45 k Maximum output voltage VOM 0.6 1.2 - Vrms THD=1% Input conversion noise voltage VNIN - 1.0 2.0 Vrms Conversion with Rg=2.2k and NAB34dB at 1kHz ALC range ALC 40 45 - dB RG=3.9k, VIN=-70dBV reference, THD=3% ALC - 0 2.5 dB VIN=-60dBV, -30dBV CS 60 75 - dB VO=0dBV, NAB34dB ALC channel balance Channel separation 2/8 BA3308 / BA3308F Audio ICs !Measurement circuit MUTE ch2 BA3308 ch1 ALC 4 5 2 3.9k 1.2k 22F 1M SW5 0.1F SW4A 33k SW2A 6 SW3A V 2 SW4B 120k 33k SW2B 1 39 10F OUTPUT2 30k V ~ 100F 30k INPUT1 INPUT1 V ~ 1 3 2 2.2k SW6A V ~ V2 V2 V ~ 3 1 2.2k SW1A V1 9 0.1F 10k 100F SW3B 10k OUTPUT1 8 1.2k VCC 10F 120k 1 39 7 330F 3 3.9k 2 220 1 SW6B 2 SW1B V ~ V1 Fig. 1 !Application example !Application example circuit PCB (copper side) BA3308 MUTE ch2 BA3308 ch1 ALC 100F C5 10F C5 10F 5 6 8 R6 OUTPUT2 INPUT1 OUTPUT1 R9 (R10) R11 (R12) 120k 4.3k 7 C6 10F R1 3.9k R3 39 C3 4 C8 330F 3 C7 22F 2 R5 18k R7 1M 1 R2 9 18k 3.9k C2 10F 1pin R8 220 R4 39 VCC 7V C4 100F INPUT2 For playback, instead of R5 and R6, connect the following NAB time constant circuit between pins 1 and 3 and 7 and 9. (40x60mm) C9 (R10) 0.027F Fig. 2 Fig.3 3/8 BA3308 / BA3308F Audio ICs !Total application circuit 220 9V 330F CC CA 33F 4.3k 100F 18k 1 6 3.9k BA3308 4 2.2F 5 39 100F 7 3 120 18k 120k 0.027F 33F 4.3k L RA CC CA SP 3 0.22F 6 9 10k 2 BA5406 8 10F 9 5 22F 4 CB 2.2F 1 7 8 1M 3.9k BIAS OSC 10k 3 CB MIC RADIO etc. 470F 47F 10F 2 120 2.2 120k 10 11 12 47F 2.2 470F SP 3 0.22F 39 0.027F 1000F RA 47F 100F L Notes: (1) Switches are in the playback positions. (2) Set the values of RA and CA depending on the characteristics of the playback/recording head. (3) The capacitor CB is for head resonance treble compensation during playback, and prevention of high-frequency noise. The recommended value is about 1000pF. (4) L and CC are a bias trap. Fig. 4 !Circuit operation (1) Recording 1) Recording amplifier (See Fig.5) The channel 1 and 2 amplifier input stages of the BA3308 (pins 8 and 2) and be direct-coupled, and the input coupling capacitors C1 and C2 are not particularly required. The voltage gain of the recording amplifier is given by GV = R5 / R3, but as a "pop" noise is generated when power is applied, (see "operation notes"), use the time constant circuit values given for C3 and R3 (C4 and R4) in the application example circuit diagram, or values close to these, and adjust the voltage gain with R5 (R6). R5 (R6) is also the DC bias feedback resistor, and is connected between pin 3 (7), and the output capacitor C5 (C6). 2) ALC (See Fig.6) The BA3308 includes a signal rectifier block and electronic potentiometers required for the ALC. In the signal rectifier block, a comparator compares the DC output voltage component of the output stage signal (pins 3 and 7) to a voltage of 4.5VF (1VF is about 0.7V, so 4.5VF is approximately 3V), and if it is above this, the comparator switches on, and changes the smoothing capacitor C7. The operating point of the amplifier's ch1 and ch2 output stages is fixed at 3VF, so when the signal output voltage is 1.5VF (an effective value of approximately 0.75V), the comparator goes on, DC signals for electronic potentiometer control are generated, and the ALC starts operating. The electronic potentiometers are connected between the input lines (pins 2 and 8) and GND, and the input signals is attenuated by the ratio of the electronic potentiometer resistances and the external resistors R1 and R2. The range of the ALC can be varied by the values of R1 and R2, but if they are too large the S/N ratio will worsen. Sufficient ALC range should be obtained with R1 and R2 values of around several k ohms. C7 and R7 connected to pin 5 set the ALC attack and recovery times. The larger the values of these constants, the longer the recovery time, and the smaller the value of C7 the shorter the attack time. 4/8 BA3308 / BA3308F Audio ICs (2) Playback (See Fig.7) During playback, the ch1 and ch2 amplifiers are used as NAB equalizer amplifiers, and time constant circuits are connected between pins 1 and 3, and 7 and 9 in the negative-feedback section to give the NAB characteristics. The voltage gain is given by: GV = | R11 + R9 / (I + jC9 * R9) | / R3 In the same way as for recording, the NAB time constant circuit is adjusted to give the required gain (to prevent generation of a "pop" noise when power is applied). The output stage (pins 3 and 7) operating point is fixed at 3VF. Therefore, as indicated in the VMAX. VS, VCC characteristic (see Fig.19), even if the VCC voltage is made larger than 5V, the maximum output voltage will not exceed 1.2V (typ.). The ALC circuit is not required for playback, so pin 5 is grounded. The S/N ratio during playback is better if the external resistors R1 and R2 that are connected to the input pins (2 and 8) for recording are switched out. BA3308 ch2 (ch1) Cont ch2 (ch1) ch1 (ch2) 2 (8) R1 (R2) 3.9k C1 (C2) 10F 1 (9) 3 (7) 5 R5 (R6) 18k R3 (R4) 39 R7 (R8) 1M C7 (C8) 22F C5 (C6) 10F C3 (C4) 100F INPUT OUTPUT Fig.5 ch1 (ch2) ch2 (ch1) Comp ch2 (ch1) Cont 4.5VF BA3308 VOUT (DC+AC) 3 (7) 5 2 (8) 3VF R7 C7 R1 (R2) Fig.6 5/8 BA3308 / BA3308F Audio ICs BA3308 A1 2 (8) C1 (C2) 10F 1 (9) R3 (R4) 39 3 (7) R9 (R10) 120k R11 (R12) 4.3k C9 (C10) 0.027F C3 (C4) 100F 5 C5 (C6) 10F OUTPUT INPUT Fig.7 !Operation notes The BA3308 has a built-in power-on mute circuit to prevent generation of a "pop" sound when the power is applied. The generation of the "pop" sound is prevented by the DC blocking capacitors C3 and C4 connected to pins 1 and 9, and the charge time required for the ripple filter capacitor C8 that is connected to pin 6. To ensure correct operation of this circuit, use the values given in the application example circuit for C3, C4, R3, R4, C8 and R8. !Application board component layout (component side) R8 C6 C8 R8 R7 C7 C6 C5 C8 BA3308 R6 C5 BA3308 R5 R4 C4 JPW R4 R3 R2 R1 C2 C1 C3 C4 (1) Recording R12 C10 C9 R11 R10 R9 JPW JPW C2 C1 R3 C3 (2) Playback Fig.8 6/8 BA3308 / BA3308F Audio ICs !Electrical characteristic curves 12 QUIESCENT CURRENT : IQ (mA) 8 6 4 2 4 6 8 10 12 14 8 6 4 2 16 0 25 50 75 Fig.9 Quiescent current vs. power supply voltage Fig.10 Quiescent current vs. ambient temperature 0.8 0.6 0.5 0.4 0.3 0.2 GVO 80 70 R5,R6=39k 60 50 R5,R6=6.8k 40 30 0 10 100 1k 10k 20 0 100k Fig.12 Total harmonic distortion vs. frequency 10 CHANNEL SEPARATION : CS (dB) 1 0.1 1 10 4 6 8 100 SIGNAL SOURCE RESISTANCE : Rg (k) Fig.15 Input conversion noise voltage vs. signal source resistance FLAT 40 NAB 30 20 10 12 1k 10k 100k 14 16 120 VCC=7V VOUT=300mVrms f=1kHz RL=10kW 100 80 60 R5,R6=18k 40 20 0 -50 -25 0 25 50 75 100 AMBIENT TEMPERATURE : Ta (C) Fig.13 Voltage gain vs. power supply voltage Fig.14 Closed loop voltage gain vs. ambient temperature 60 VCC=7V GV=52dB VOUT=1Vrms RL=10k Rg=0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 10 100 POWER SUPPLY VOLTAGE : VCC (V) 0 VCC=7V GV=52dB RL=10kW DIN AUDIO 0.1 0.01 2 OUTPUT VOLTAGE : VOUT (dBV) 0.1 50 Fig.11 Voltage gain vs. frequency VOUT=300mVrms f=1kHz 90 RL=10k 0.7 GVO 60 FREQUENCY : f (Hz) 100 VCC=7V VOUT=1Vrms RL=10k NAB 0.9 70 0 10 100 POWER SUPPLY VOLTAGE : VCC (V) FREQUENCY : f (Hz) INPUT CONVERSION NOISE VOLTAGE : VNIN (Vrms) -25 AMBIENT TEMPERATURE : Ta (C) 1.0 80 10 0 -50 CLOSED LOOP VOLTAGE GAIN : GVO (dB) 2 10 100 1k 10k 100k VCC=7V f=1kHz GV=52dB 40 10 8 6 20 ch2 VOUT 0 4 ch1 ch2 -20 2 ch1 THD -40 -80 -60 -40 -20 -0 FREQUENCY : f (Hz) INPUT VOLTAGE : VIN (dBV) Fig.16 Channel separation vs. frequency Fig.17 ALC characteristics 0 20 TOTAL HARMONIC DISTORTION : THD (%) 10 VCC=7V VOUT=300Vrms RL=10K 90 VOLTAGE GAIN : GV (dB) 12 0 0 TOTAL HARMONIC DISTORTION : THD (%) 100 VCC=7V 14 VOLTAGE GAIN : GV (dB) QUIESCENT CURRENT : IQ (mA) 16 7/8 BA3308 / BA3308F 1.6 VOUT 1 0.1 THD 0.01 -80 -70 -60 -50 VCC=7V f=1kHz GV=52dB RL=10k -40 -30 -20 2 f=1kHz THD=1% RL=10k 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 2 4 6 8 10 12 14 16 INPUT VOLTAGE : VIN (dBV) POWER SUPPLY VOLTAGE : VCC (V) Fig.18 Input/output characteristics Fig.19 Maximum output voltage vs. power supply voltage MAXIMUM OUTPUT VOLTAGE : VOM (Vrms) 10 MAXIMUM OUTPUT VOLTAGE : VOM (Vrms) OUTPUT VOLTAGE : VOUT (Vrms) TOTAL HARMONIC DISTORTION : THD (%) Audio ICs VCC=7V f=1kHz THD=1% 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 100 1k 10k LOAD RESISTANCE : RL () Fig.20 Maximum output voltage vs. load resistance !External dimensions (Units : mm) BA3308 BA3308F 8.70.2 0.8 1.3 0.30.1 8 1 7 4.40.2 14 1.27 0.150.1 0.6 1.50.1 9 2.54 0.11 6.20.3 2.80.2 1.2 5.80.2 1 3.50.5 10.50.5 21.80.2 0.40.1 0.3Min. 0.15 SIP9 SOP14 8/8