TLH12327 – 4

TLH12327 – 5

TLH12327 – 6

FIGURE 5 Large Signal Frequency Response

TLH12327 – 7

FIGURE 6 Pulse Response

Theory of Operation

The LM2406 is a high voltage monolithic triple CRT driver

suitable for VGA and SVGA display applications

The

tion The part is housed in the industry standard 11-lead

TO-220 molded plastic power package

The circuit diagram of the LM2406 is shown in

Figure 1 Q1

and R2 provide a conversion of input voltage to current

while Q2 acts as a common base or cascode amplifier stage

to drive the load resistor R1 Emitter followers Q3 and Q4

isolate the impedance of R1 from the capacitance of the

CRT cathode and make the circuit relative insensitive to

the collector time constant formed by the resistor R1 and

associated capacitance of Q2 Q3 Q4 and stray layout ca-

pacitance Transistor Q6 and resistors R7 and R8 provide

biasing to the output emitter-follower stage to reduce cross-

over distortion at low signal levels while R3 provides a DC

bias offset to match the output level characteristics of the

preamplifier stage

Figure 2 shows a typical test circuit for evaluation of the

LM2406 This circuit is designed to allow testing of the

LM2406 in a 50X environment such as a pulse generator

and a scope or a network analyzer In this test circuit two

resistors in series totaling 495 kX form a 1001 wideband

low capacitance probe when connected to a 50X cable and

load The input signal from the generator is AC coupled to

base of Q2 (See

Figure 2 )

3