- 您現(xiàn)在的位置：買賣IC網 > PDF目錄30745 > LM2202N/NOPB (NATIONAL SEMICONDUCTOR CORP) 1 CHANNEL, VIDEO AMPLIFIER, PDIP20 PDF資料下載
參數(shù)資料
| 型號： | LM2202N/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 1 CHANNEL, VIDEO AMPLIFIER, PDIP20 |
| 封裝： | N20A |
| 文件頁數(shù)： | 13/17頁 |
| 文件大小： | 416K |
| 代理商： | LM2202N/NOPB |
Circuit Description (Continued)
providesa6dB gain adjustment range. This feature is nec-
essary for RGB applications where independent gain adjust-
ment of each channel is required.
The brightness or black level clamping requires a “sample
and hold” circuit which holds the DC bias of the video ampli-
fier constant during the black level reference portion of the
video waveform. Black level clamping, often referred to as
DC restoration, is accomplished by applying a back porch
clamp signal to the clamp gate input pin (pin 14). The clamp
comparator is enabled when the clamp signal goes low dur-
ing the black level reference period (see
Figure 2). When the
clamp comparator is enabled, the clamp capacitor con-
nected to pin 12 is either charged or discharged until the volt-
age at the minus input of the comparator matches the volt-
age set at the plus input of the comparator. During the video
portion of the signal, the clamp comparator is disabled and
the clamp capacitor holds the proper DC bias. In a DC
coupled cathode drive application, picture brightness func-
tion can be achieved by varying the voltage at the compara-
tor’s plus input. Note that the back porch clamp pulse width
(t
W in Figure 2) must be greater than 100 ns for proper op-
eration.
VIDEO AMPLIFIER SECTION (Input Stage)
A simplified schematic of LM2202’s video amplifier input
stage is shown in
Figure 3. The 5.4V zener diode, Q1, Q6
and R2 bias the base of Q7 at 2.6V. The AC coupled video
signal applied to pin 6 is referenced to the 2.6V bias voltage.
Transistor Q7 buffers the video signal, V
IN, and Q8 converts
the voltage to current. The AC collector current through Q8 is
I
C8 = VIN/R9. Under maximum gain condition, transistors Q9
and Q11 are off and all of I
C8 flows through the load resistors
R10 and R11. The maximum signal gain at the base of Q13
is, A
V1
= (R10 + R11)/R9 = 2. Signal attenuation is
achieved by varying the base drive to the differential pairs
Q9, Q10 and Q11, Q12 thereby unbalancing the collector
currents through the transistor pairs. Base of Q10 is biased
at 5.3V by externally connecting pin 1 to pin 20 through a
100
resistor. Pin 2 is connected to pin 3 through a 100 re-
sistor. Adjusting the contrast voltage at pin 8 produces a con-
trol voltage at pin 3 which drives the base of Q9. By varying
the voltage at the base of Q9, Q8’s collector current (I
C8)is
diverted away from the load resistors R10 and R11, thereby
providing
signal
attenuation.
Maximum
attenuation
is
achieved when all of I
C8 flows through Q9 and no current
flows through the load resistors.
The differential pair Q11 and Q12 provide drive control.
Q12’s base is internally biased at 7.3V. Adjusting the voltage
at the drive control input (pin 9) produces a control voltage at
the base of Q11. With Q9 off and Q12 off, all of I
C8 flows
through R10, thus providing a gain of A
V1 = (R10/R9) x VIN
= 1. Drive control thus provides a 6 dB attenuation range.
DS012591-8
FIGURE 2. Block Diagram of the LM2202 Video Amplifier
with Contrast and Brightness (Black Level) Control
www.national.com
5
相關PDF資料 |
PDF描述 |
|---|---|
| LM2202M/NOPB | 1 CHANNEL, VIDEO AMPLIFIER, PDSO20 |
| LM22672QMR-ADJ | 1.8 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO8 |
| LM236ZT | 1-OUTPUT TWO TERM VOLTAGE REFERENCE, 2.49 V, PBCY3 |
| LM236DT | 1-OUTPUT TWO TERM VOLTAGE REFERENCE, 2.49 V, PDSO8 |
| LM236Z-AP | 1-OUTPUT TWO TERM VOLTAGE REFERENCE, 2.49 V, PBCY3 |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM220K12 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
| LM220K15 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
| LM220K5 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
| LM2-20V2-SI | 功能描述:基本/快動開關 Foot Switch RoHS:否 制造商:Omron Electronics 觸點形式:SPDT 執(zhí)行器:Lever 電流額定值:5 A 電壓額定值 AC:250 V 電壓額定值 DC:30 V 功率額定值: 工作力:120 g IP 等級:IP 67 NEMA 額定值: 端接類型:Wire 安裝:Panel |
| LM220Z | 制造商:SEOUL 制造商全稱:Seoul Semiconductor 功能描述:GREEN OVAL LAMP LED |
發(fā)布緊急采購，3分鐘左右您將得到回復。