LM1201N National Semiconductor, LM1201N Datasheet - Page 8

• Manufacturer Part Number: LM1201N
• Description: IC VIDEO AMP SYSTEM 16DIP
• Manufacturer: National Semiconductor

Specifications of LM1201N

• Applications: General Purpose
• Number Of Circuits: 1
• -3db Bandwidth: 170MHz
• Current - Supply: 45mA
• Current - Output / Channel: 28mA
• Voltage - Supply, Single/dual (±): 10.8 V ~ 13.2 V
• Mounting Type: Through Hole
• Package / Case: 16-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *LM1201N; LM1201

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Figure 7 also shows how the contrast control circuit is con-
Figure 8 is a simplified schematic of the clamp gate and
Circuit Description
figured Resistors R23 R24 diodes D3 D4 and transistor
Q13 are used to establish a low impedance zero TC half
supply voltage reference at the base of Q14 The differential
amplifier formed by Q15 Q16 and feedback transistor Q17
along with resistors R27 R28 establish a differential base
voltage for Q3 and Q4 in Figure 6 When externally adding
or subtracting current from the collector of Q16 a new dif-
ferential voltage is generated that reflects the change in the
ratio of currents in Q15 and Q16 To provide voltage control
of the Q16 current resistor R29 is added between the Q16
collector and pin 4 A capacitor should be added from pin 4
to ground to prevent noise from the contrast control pot
from entering the IC
clamp comparator section of the LM1201 The clamp gate
circuit consists of a PNP input buffer transistor (Q18) a PNP
emitter coupled pair referenced on one side to 2 1V (Q19
Q20) and an output switch (Q21) When the clamp gate
input at pin 5 is high (
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FIGURE 8 Simplified Schematic of LM1201 Clamp Gate and Clamp Comparator Circuits
l
1 5V) the Q21 switch is on and
(Continued)
8
shunts the I1 1mA current to ground When pin 5 is low
(
source is mirrored or ‘‘turned around’’ by reference diode
D5 and Q26 to provide a 1mA current source for the clamp
comparator The inputs to the comparator are similar to the
clamp gate input except that an NPN emitter coupled pair is
used to control the current which will charge or discharge
the clamp capacitor at pin 2 PNP transistors are used at the
inputs because they offer a number of advantages over
NPNs PNPs will operate with base voltages at or near
ground and will usually have a greater reverse emitter-base
breakdown voltage (BVebo) Because the differential input
voltage to the clamp comparator during the video scan peri-
od could be greater than the BVebo of NPN transistors
resistor R34 with a value one half that of R33 or R35 is
connected between the bases of Q23 and Q27 This resis-
tor will limit the maximum differential input to Q24 Q25 to
approximately 350 mV The clamp comparator common
mode range extends from ground to approximately 9V and
the maximum differential input voltage is V
k
1 3V) the Q21 switch is off and the I1 1mA current
CC
and ground
TL H 10006 – 8