 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
EL4390C Datasheet(PDF) 9 Page - Elantec Semiconductor |
|
||||||||||||||||||||||||||||||
EL4390C Datasheet(HTML) 9 Page - Elantec Semiconductor |
|
|
9 / 16 page  EL4390C Triple 80 MHz Video Amplifier with DC Restore Applications Information Circuit Operation Each channel of the EL4390 contains a current feedback amplifier and a TTLCMOS compatible clamp circuit The current that the clamp can source or sink into the non-inverting input is ap- proximately I e (VCLAMP b VINa) 120 So when the non-inverting input is at the same voltage as the clamp reference no current will flow and hence no charge is added to the capaci- tor When there is a difference in voltage current will flow in an attempt to cancel the error AT THE NON-INVERTING input The amplifier’s offset voltage and (IBb c RF) DC errors are not cancelled with this loop It is purely a method of adding a controlled DC offset to the signal As well as the offset voltage error which goes up with gain and the IBb c RF error which drops with gain there is also the IBa error term Since the amplifier is capacitively coupled this small current is slowly integrated and shows up as a very slow ramp voltage Table below shows the output voltage drift in 60 mS for various values of coupling capacitor all assuming the very worst IBa current Table 1 Charge Storage Capacitor Value vs Droop and Charging Rates Cap Value Droop in Charge in Charge in (nF) 60mS (mV) 2mS (mV) 4mS (mV) 10 30 400 800 22 136 182 364 47 64 85 170 100 30 40 80 220 136 18 36 In normal circuit operation the picture content will also cause a slow change in voltage across the capacitor so at every back porch time period these error terms can be corrected When a signal source is being switched eg from two different surveillance cameras it is recom- mended to synchronize the switching with the vertical blanking period and to drive the HOLD pin (pin 6) low during these lines This will en- sure that the system has been completely re- stored regardless of the average intensity of the two pictures Application Hints Figures12 shows a three channel DC-restoring system suitable for R-G-B or Y-U-V component video or three synchronous composite signals Figure 1 shows the amplifiers configured for non- inverting gain and Figure 2 shows the amplifiers configured for inverting gains Note that since the DC-restoring function is accomplished by clamping the amplifier’s non-inverting input during the back porch period any signal on the non-inverting input will be distorted For this reason it is recommended to use the inverting configuration for composite video since this avoids the color burst being altered during the clamp time period Since all three amplifiers are monolithic they run at the same temperature and will have very similar input bias currents This can be used to advantage in situations where the droop voltage needs to be compensated since a single trim cir- cuit can be used for all three channels A 560K X or similar value resistor helps to isolate each sig- nal See Figure 2 The advantage of compensat- ing for the droop voltage is that a smaller capaci- tor can be used which allows a larger level resto- ration within one line See Table 1 for values of capacitor and chargedroop rates 9 |
Similar Part No. - EL4390C |
|
Similar Description - EL4390C |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
