The internal principle and music circuit of HA12091

This is the internal circuit schematic diagram of HA12091. As shown in the figure, the mutually independent left and right channels have a completely symmetrical
circuit structure, each consisting of a controllable low-pass filter, a controllable high-pass filter, an analog switch, a controllable recording/playback processing circuit, and a
controllable selection switch . The circuit and the playback amplifier are composed of o
    When the Dolby switch selection control terminal (pin 6) is placed at high level (9~14V), the controllable selection switch and
analog switch circuit in the circuit channel work in series connection state respectively. The left and right channels of the circuit enter the Dolby Type-C operating state with greatly reduced noise
. When the Dolby switch selection terminal (pin 6) is placed at the mid-level (6~6.8V), the controllable recording processing circuit
and the controllable selection switch circuit in the circuit channel will work in the adder (or subtractor) state, causing the left and right channels of the circuit to enter the encoding and decoding working state of Dolby B-type
noise reduction . When the Dolby switch selection terminal (pin 6) is placed at low level (<4V), the sub-channel circuit in
the does not work (the controllable selection switch and analog switch circuit are in a blocking state), allowing rC to work In
the non-noise reduction state.
    In order to ensure that the gain difference of the entire Dolby BC noise reduction system is zero during encoding (recording) and decoding (playback) operations,
the encoder and decoder in the circuit sub-channel share the same set of circuits. As long as the specially set recording Aoyin switch
circuit in the IC is switched and controlled, the noise reduction function of different working states of recording and playback can be realized.
    The main electrical parameters of HA12091 are listed in Table 5-4. It has a wide power supply voltage range, the highest power supply voltage can
reach 16V, and the allowed power consumption is 940mW.
    The recording working status of the LC is determined by the level set by pins 39 and 40. Among them, pin 39 is the left channel recording/
playback selection terminal, and pin 40 is the right channel recording alarm selection terminal.
    When pins 39 and 40 of IC are both placed at high level, the left and right channel noise reduction systems are working in recording (encoding) state
. Taking the right audio signal as an example, the recording signal is input to pin 1 of the IC via the coupling capacitor C1. The controllable recording/processing circuit in the IC works
in the adder state, and uses the frequency band sliding of the controllable high-pass filter to complete Dolby B Type noise reduction function, LC pin 22 outputs
the noise-reduced recording signal.
    When pins 39 and 40 of the LC are both placed at low level, the left and right channel noise reduction systems are working in the playback (decoding)
state. Taking the right channel as an example, the playback signal is input to pin 3 of the IC through the coupling capacitor. The controllable recording/playback processing
circuit works in the subtractor state. After completing the Dolby B-type noise, the playback signal is lo.9 pin output.