G(dB)

100k

1M

10M

+1

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

f(MHz)

Figure 1 : Video Bandwith

90%

10%

50 ns/div. ; uncal

Figure 2 : Fall Time

90%

10%

50 ns/div. ; uncal

Figure 3 : Rise Time

P. C. Board

The best performance of the RGB video amplifier

can be obtained only with a carefully designed P.C.

board. The layout of the printed circuit must be

realized to achieve the best possible symmetry of

the three channels.

Output to input capacitances are of particular im-

portance. The input-output capacitances, in paral-

lel with the relative high feedback resistances,

create poles in the closed loop transfer function.

To optimize the band response and to minimize the

channels crosstalk a low parasitic capacitance

feedback resistors of not inductive type is neces-

sary.

Capacitive coupling from the output of an amplifier

and the input of another one may induce excessive

crosstalk. It is advisable to keep the amplifier out-

puts away from amplifier inputs.

The small size of the P.C. board allows you to

mount the TDA8153 directly beside the picture tube

socket, to minimize the capacitances of the con-

nections between the video amplifiers and the pic-

ture tube cathodes.

The capacitors connected in parallel with the input

resistors compensate the effects of the distributed

constants of the printed circuit on the step response

times. Their values must be selected on the basis

of the layout and can be considered as function of

the printed circuit.

The three capacitors (C9, C10, C11) between the

amplifier outputs and the feedback resistors re-

duces the noise effect on the cut-off control, their

value, of course, depends on the noise amplitude

and spectrum coming from the I.F. video stage.

To prevent possible oscillation problems, it is nec-

essary to place the high voltage filter capacitor (C3)

as near as possible to the IC ground and the latter

must be of a substantial width.

APPLICATION NOTES

TDA8153

9/11