LM1207N National Semiconductor, LM1207N Datasheet - Page 11

• Manufacturer Part Number: LM1207N
• Manufacturer: National Semiconductor

Specifications of LM1207N

• Lead Free Status / RoHS Status: Not Compliant

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 LM1207 Video Amplifier
(Continued)
TL H 11881 – 15
11
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 LM1207 is not degraded by the 30
ever if EMI is a concern this resistor can be increased to
well over 100
become longer DC bias to the input pin is provided by Q5
and its associated 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
collector 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
LM1207 The bias voltage goes through R6 a 20k resistor
to the video input at pin 6 R4 and R6 are of the same value
resistor The resistor is added to limit the current
CC
or drop below ground The performance of the
where the rise and fall times will start to
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resistor How-
TL H 11881– 14
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