Five-way electronic switch

It is a multifunctional preamplifier using an electronic switch. It consists of a light-touch five-way electronic switch and
a DC servo RIAA ultra-low distortion high-speed amplifier. It can be connected through the volume and tone control circuit and the post-stage power amplifier
circuit. Figure 3-24 is a light-touch five-way electronic switch composed of TC9152.
    In Figure 3-23, VT3~expands form a common source-common emitter differential input circuit, and VTc and VT2 are mirror constant current source
loads. IC1 is the main amplifier, Vr7 and VT8 are push-pull outputs. IC2 forms a DC servo circuit. Island, C6, Rl2 and R13
can determine the DC servo time constant. R, R,, C3, and C4 form a phono equalization network. ‰, R9 is a DC feedback circuit
, which can be used to adjust the DC gain. In the circuit, the differential input field effect transistor is an American-made NPD5565 field effect transistor, which is a
low-noise, high-transconductance transistor with a withstand voltage of 55v-j and a range of 10 to 30rnAr.
Field effects Tube.
    The audio source switching switch adopts Toshiba's audio-specific light-touch electronic analog switch (not comparable to ordinary digital switches
), which eliminates the impact noise and poor contact caused by mechanical switching switches. ∞152 can
work normally under single or dual power supplies. The working voltage range is 7.5~30V0. Pin 2412 is connected to the positive and negative power supplies respectively; pins 6~10 are
the L channel input terminals of the first to fifth switches; 18~ Pin 14 is the R channel input terminal of the first to fifth groups of switches;
pin 1113 is the L and R channel output terminal respectively; pins 23 to 19 are the control terminals of the first to fifth groups of switches respectively, which correspond to
FUNER ( Tuner), CD (CD player), TAPE (tape recorder), AUX (auxiliary input), PHONO
(record player), when one of the pins is triggered by high level v+, the corresponding L and R channel switches are turned on , the other four sets of switches
are disconnected, and at the same time, this pin outputs a high level to drive the LED to display the working status. The driving ability of these five pins is strong, and
the output current can reach 20mA; pin 2 is the function prohibition terminal and is connected to zero. When the level is low, the switch control pins 19~23 have no effect and are
usually connected to the positive power supply; pin 3 is externally connected to Rx and Cx to determine the clock frequency. The oscillation frequency can be determined by the formula fosc=1/1,5RxCr
, which is generally 20Hz~100H. The oscillator starts to oscillate after the input is applied, and stops oscillating after five clock pulses are input
. Pin 4 is the analog switch shutdown control terminal. It is usually connected to low level. When connected to high level, all analog switches are turned off.
This pin can be used in combination with multiple 152s; pin 5 is the squelch control output terminal. It outputs
a high level is used to drive the squelch switch to cut off the output signal (the rate circuit is not used, so there is no Squelch function), the squelch signal output
time can be determined by the oscillation frequency table: T pin = 1/f × 4 seconds; in addition, adding a remote control signal trigger
conversion circuit on pins 23 ~ 19 can also realize remote control operation of the circuit .