LM1205N National Semiconductor, LM1205N Datasheet - Page 10

• 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 8 is a simplified schematic of one of the three video
Functional Description
Circuit Description
VIDEO AMPLIFIER INPUT STAGE
amplifiers input stage along with the recommended external
components The IC pin numbers are circled and all external
components are shown outside the dashed line The video
FIGURE 7 Timing Diagram
FIGURE 6 Block Diagram of LM1205 Video Amplifier
(Continued)
TL H 11831– 11
10
input is applied to pin 6 via a 10 F coupling capacitor and a
30
through the input pin should an applied voltage surge rise
above V
LM1205 is not degraded by the 30
EMI is a concern this resistor can be increased to well over
100
er DC bias to the input pin is provided by Q5 and its associ-
ated input circuitry Z1 is a 5 6V zener that generates the
input bias voltage Q1 is a buffer to the zener reference
voltage with 5 0V generated at its emitter Q3 and Q4 are
connected as diodes Q2 is close to being a diode in this
circuit This configuration will give about 2 0V at the collec-
tor of Q2 R2 and R3 are a voltage divider setting the base
of Q5 to about 3 5V This sets the emitter of Q5 to about
2 8V the bias voltage of the video input This bias voltage is
necessary to assure that the entire video signal stays within
the active operating region of the LM1205 The bias voltage
goes through R6 a 20k resistor to the video input at pin 6
R4 and R6 are of the same value and R4 is used to com-
resistor The resistor is added to limit the current
where the rise and fall times will start to become long-
CC
or drop below ground The performance of the
resistor However if
TL H 11831 – 10