Monolithic Triple 9.5Ns Crt Driver; Theory Of Operation - NEC MultiSync FE700 Serviceanleitung

10. Monolithick triple 9.5ns CRT driver
General Description
The LM2439 is an integrated high voltage CRT driver circuit designed for use in color monitor applications.
The IC contains three high input impedance, wide band amplifiers which directly drive the RGB cathodes of
a CRT. Each channel has its gain internally set to -14 and can drive CRT capacitive loads as well as
resistive loads present in other applications, limited only by the package's power dissipation.
The IC is packaged in an industry standard 9-lead TO-220 molded plastic power package. See Thermal
Considerations section.
Features
• Dissipates approximately 50% less power than the LM2406
• Well matched with LM1279 video preamp
• 0V to 5V input range
• Stable with 0 pF–20 pF capacitive loads and inductive peaking networks
• Convenient TO-220 staggered lead package style
• Standard LM243X Family Pinout which is designed for easy PCB layout
Applications
• 1024 x 768 Displays up to 70 Hz Refresh
• Pixel clock frequencies up to 75 MHz
• Monitors using video blanking
Schematic and Connection Diagrams

Theory of Operation

The LM2439 is a high voltage monolithic three channel CRT driver suitable for high resolution display
applications. The LM2439 operates with 80V and 12V power supplies. The part is housed in the industry
standard 9-lead TO-220 molded plastic power package.
The circuit diagram of the LM2439 is shown in Figure 1. The PNP emitter follower, Q5, provides input
buffering. Q1 and Q2 form a fixed gain cascode amplifier with resistors R1 and R2 setting the gain at -14.
Emitter followers Q3 and Q4 isolate the high output impedance of the cascode stage from the capacitance of
the CRT cathode which decreases the sensitivity of the device to load capacitance. Q6 provides bi-asing
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