Cascode Ckt - Acer V551 Service Manual

Acer V551 (new) CRT Monitor Service Guide

(4) Cascode CKT

(a) Output stage adopts cascode circuit Its purpose is to amplify the signal which has
been processed by MM1375XD to a enough amplitude of Vpp, then display on the
CRT. The criteria to select a cascode transistor is the smaller the value of Cob and the
bigger the value of Ft is better.This circuit adopts HSD1609. Cob=3.8pF, ft=140MHZ.
(b) Cascode CKT concludes 3 band amplification.
Mean Freq.: capacitance open, inductance short. The gain = Rc /Re
High Freq.: (R gun),peaking coil L104,L105,R115,C113,R119
Over Freq. Compensation: (R gun),C161,R161.
12V
B O/P
R114
56
Q101
HSD1609
C112
0.1U
R113
(OPEN)
R116
Q102
30
H945
C113
82P
R117 C161
50V
390 150p
(D)
50V
(D)
R118 R161
R119
100 8.2K
33
1/2W
Confidence and Property
Chapter 2 Circuit Operation Theory
L105
2.7U
R115
1.6K
1/4W
R151
+75V
1.2K
3W
R171
(OPEN)
DC RESTORE
L104
15UH
D101
1SS83
11