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參數(shù)資料
| 型號： | LMC1983CIN |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻控制 |
| 英文描述： | Pushbutton Switch; Actuator Style:Rectangular; Circuitry:DPST-1NO/1NC; Switch Operation:On-(On); Contact Current Max:5A; Collar Shape:Rectangular; Features:Illuminated; Leaded Process Compatible:Yes; Mounting Type:PCB |
| 中文描述： | 2 CHANNEL(S), TONE CONTROL CIRCUIT, PDIP28 |
| 封裝： | 0.600 INCH, PLASTIC, DIP-28 |
| 文件頁數(shù)： | 7/14頁 |
| 文件大?。?/td> | 331K |
| 代理商： | LMC1983CIN |
General Information
(Continued)
Application Information
INPUT SELECTOR
The LMC1983’s input selector and mode control are shown
in Figure 2 The input selector selects one of three stereo
signal sources or a mute function with typical attenuation of
100 dB. The selected signals are then sent to a mode control
matrix. As shown in Table 1 the matrix provides normal ste-
reo or can direct any given channel to both LEFT or RIGHT
SELECT OUTPUTs. The third matrix mode is normal stereo.
The control matrix output is buffered and appears on each
channel’s respective SELECT OUT pin (7, 22). Switching
noise is kept to a minimum when mute is selected by using
a 50 k
bias resistor.
Noise performance is optimized through the use of emitter
followers in the mode control matrix’s output. Internal 50 k
resistors are connected to each input selector pin to provide
the proper bias point for the emitter follower buffers. Each in-
ternal 50 k
bias resistor is connected to a common
half-supply (V
+
/2) source. This produces a voltage at pins 7
and 22 (SELECT OUT) that is 1.4V below V
+
/2 (typically
3.1V with V
+
= 9V). Since a DC voltage is present at the in-
put pins (4, 5, 6, 23, 24, and 25), input signals should be AC
coupled through a 1 μF capacitor.
The output signal at pins 7 and 22 can be used to drive ex-
teral audio processing circuits such as noise reduction
(LM1894–DNR or Dolby) or graphic equalizers (LMC835). It
is important that if any noise reduction is used it be placed
ahead of any tone controls or equalizers in the external cir-
cuit path to preserve the frequency spectrum of the selected
input signal. Otherwise, any frequency equalization could
prevent the proper operation of the noise reduction circuit. If
no external processor is used, a capacitor should be used to
couple the SELECT OUT signals directly to pins 8 and 21,
respectively.
MINIMUM LOAD IMPEDANCE
The LMC1983 employs emitter-followers to buffer the se-
lected stereo channels. The buffered signals are available at
pins 7 and 22 (SELECT OUT). The SELECT OUT buffers op-
erate with a typical bias current of 1 mA.
The Electrical Specifications table lists a maximum input sig-
nal of 2.0 V
(2.8 V
) for 1% THD at the SELECT OUT
pins. This distortion level is achieved when the minimum AC
load impedance seen by the SELECT OUT pins is 2.5 k
(2.5V/1 mA). Using lower load impedances results in clipping
DS011279-3
FIGURE 1. Typical Application
www.national.com
7
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相關代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMC1983CIV | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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| LMC1992 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:LMC1992 Digitally-Controlled Stereo Tone and Volume Circuit with Four-Channel Input-Selector |
| LMC1992CCN | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:LMC1992 Digitally-Controlled Stereo Tone and Volume Circuit with Four-Channel Input-Selector |
| LMC200 | 制造商:Black Box Corporation 功能描述:14 SLOT POWER CHASSIS W/1 POWE |
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