LM1205N National Semiconductor, LM1205N Datasheet - Page 18

• Manufacturer Part Number: LM1205N
• Description: IC VIDEO AMP 130MHZ RGB 28DIP
• Manufacturer: National Semiconductor

Specifications of LM1205N

• Applications: General Purpose
• Number Of Circuits: 3
• -3db Bandwidth: 130MHz
• Current - Supply: 90mA
• Current - Output / Channel: 28mA
• Voltage - Supply, Single/dual (±): 10.8 V ~ 13.2 V
• Mounting Type: Through Hole
• Package / Case: 28-DIP (0.600", 15.24mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *LM1205N

Figure 14 also shows the power and ground pins to the
Figure 15 is the schematic of the demonstration board de-
Circuit Description
age of Q29 There are also four diode drops from the base
of Q30 to the output pin 20 Therefore during blanking pin
20 will be less than 100 mV above ground enabling the
designer to blank at the cathode of the CRT R23 is added
to quickly turn off Q25 by discharging its base when the
blanking signal is removed
LM1205 All the V
nally connected together A 0 1
be located close to each pin and connected to ground Fur-
ther bypassing is done by a 100 F capacitor This capaci-
tor needs to be located on the board close to the LM1205
Pin 23 is the V
series with the input power A 10
capacitors must be located close to pin 23 Correct bypass-
ing of pin 23 is very important If the bypassing is not ade-
quate then the outputs of the LM1205 will have ringing or
even worse they may oscillate The ground side of the by-
pass capacitors at pin 23 must be returned to a ground
plane with no interruptions from other traces between these
capacitors and the ground pins 21 and 24 of the LM1205
Applications of the LM1205
signed at National Figure 16 is the actual layout of the dem-
onstration board
FIGURE 14 Simplified Schematic of LM1205 Video Amplifier Output Stage with Blank Circuit
CC2
CC1
pin This pin may need a 10
Note that the schematic shown in
pins (pins 3 11 22 25) are all inter-
(Continued)
F bypass capacitor must
F and a 0 1
resistor in
F bypass
18
Figure 15 is almost identical to the schematic shown in Fig-
ure 4 The only difference between the two schematics is
that in Figure 15 each channel has individual adjustments
for both drive and cutoff making this circuit a good design
for monitor applications Each CRT will have a slightly differ-
ent cutoff voltage for each color making it necessary to
provide separate adjustments in order to accurately set the
cutoff for each color The gain of each color of the CRT is also
slightly different if the color temperature of the display is to
be accurately set then each channel of the LM1205 must
have individual gain adjustments Thus each channel has its
own drive control Once the drive control is set the gain
between the three color channels will closely track as the
contrast is adjusted All the jumpers needed to design a
single sided PC board are shown in the schematic The re-
sistors and jumpers with no reference designation are the
connections between the PC board and the connectors
mounted on the PC board CN1 thru CN8 are BNC connec-
tors
A 30
voltage surge may occur at these inputs when either the
inputs are first connected to another system or when the
system is powered up before the monitor is turned on If this
voltage surge exceeds the supply voltage (at ground poten-
tial if the monitor is not powered up) of the LM1205 or goes
below ground current will flow through the parasitic devices
of the LM1205 This current is limited by the 30
preventing a potential catastrophic failure A 100
resistor is in series with each of the video inputs A
TL H 11831 – 18
resistors
resistor