Audio ICs Band-pass filter for spectral analyzers BA3830S The BA3830S is a 61 band band-pass filter for spectral analyzer displays with internal recording indicator output. All of the capacitors comprising the filter are internal capacitors, making it possible to significantly reduce the number of attached components. This enables configuration of compact sets with a high level of reliability. Applications CD radio cassette players, mini-components, car stereos Features 1) Six internal band-pass filters for spectral analyzers 2) Internal input / output for recording indicators 3) Internal capacitors reduce the number of attachments. Absolute maximum ratings (Ta = 25C) Recommended operating conditions (Ta = 25C) 583 Audio ICs Block diagram 584 BA3830S Audio ICs BA3830S Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 5V, RL = 10MΩ, Rφ1 = 270kΩ, Rφ2 = 270kΩ) 585 Audio ICs Measurement circuit 586 BA3830S Audio ICs Circuit operation (1) LINE and REC input circuits The LINE and REC input circuits are configured as differential amplifiers, and the gain can be set to any desired value using an external resistor. The input impedance is determined by the external resistor. BA3830S (2) Bias circuit A bias voltage of VCC / 2 is applied to each of the circuits. Since the output stage uses a push-pull configuration, a stable bias source can be obtained. (3) BPF circuit This is a circuit that selects the required frequency component from the input signal and amplifies it. With this configuration, no external capacitor is needed. In addition, the center frequency is set based on the current, so f01 and f02 to f06 can be set individually, using separate external resistors (pins1 and 2). Q is set to 4.5V (Typ.). 587 Audio ICs (4) DET circuit This circuit carries out phase detection on the signal selected and amplified by the BPF, and holds it at the peak level. It is configured so that all of the capacitors are internal. The charge that was charged by the internal capacitors in the DET circuit is set to be discharged at 75ms / V (Typ.), but in order to eliminate any effects of disparity, a reset circuit is also included. (5) Output section circuit The signal level held at peak level by the DET undergoes V / I conversion and is output. Since the next stage supports MOS (high-input impedance), there is a resistance of 33.9kΩ (44.3kΩ for REC output only) between the output pin and the GND in the IC, so the output value changes based on the input impedance. 588 BA3830S Audio ICs BA3830S Application example Operation notes (1) Precautions concerning the load resistance The various characteristics were measured at the output resistance value of 10MΩ noted in the specifications manual. Moreover, because the output of this IC supports the MOS configuration, be aware that it is current output, and the output changes depending on the input impedance at the next stage. (2) Precautions concerning the RESET capacitor If the reset function is to be used, a capacitor of at least 3300pF is required for RESET C (pin 7). Failing to connect this capacitor can result in erroneous displays, so make sure a sufficient capacitance is provided. (3) Precautions concerning the coupling capacitor When determining the polarity of the input electrolytic coupling capacitor, the potential relation with the other end of the coupling must be taken into consideration. 589 Audio ICs Electrical characteristic curves External dimensions (Units: mm) 590 BA3830S