Tektronix TDS 520A - Page 75

Circuit Description
Theory of Operation
3Ć2
Attenuators;(0"3(207 (, 2'$ 22$,3 2-0 1$*$"21 2'$ (,.32 "-3.*(,& 2$0+(:
, 2(-, ,# 2'$ 22$,3 2(-, % "2-0 '$ .0-"$11-0 1712$+ !7 5 7 -% 2'$
"/3(1(2(-, 1712$+ "-,20-*1 2'$ 22$,3 2-01 -0 $6 +.*$ (% 9W (,.32 2$0+(:
, 2(-, (1 1$*$"2$# ,# 2'$ (,.32 (1 -4$0*- #$# 2'$ .0-"$11-0 1712$+ 15(2"'$1
2'$ (,.32 2- 2'$ 9W .-1(2(-,
Probe Coding Interface;0-!$ "-#(,& (,2$0% "$ 1(&, *1 . 11 2'0-3&'
2'$  22$,3 2-0 2- 2'$ "/3(1(2(-, 1712$+ 5'$0$ 2'$7 0$ 1$,1$# ,#
"-,20-**$#
Acquisition System;'$ "/3(1(2(-, 1712$+ +.*(%($1 2'$ (,.32 1(&, *1
"-,4$021 2'$+ 2- #(&(2 * 1(&, *1 ,# "-,20-*1 2'$ "/3(1(2(-, .0-"$11 3,#$0
#(0$"2(-, -% 2'$ .0-"$11-0 1712$+ '$ "/3(1(2(-, 1712$+ (,"*3#$1 2'$ 20(&:
&$0 "/3(1(2(-, 2(+(,& ,# "/3(1(2(-, +-#$ &$,$0 2(-, ,# "-,20-* "(0"3(207
D1 Bus;'$ "/3(1(2(-, 1712$+ . 11$1 2'$ #(&(2 * 4 *3$1 0$.0$1$,2(,& 2'$
"/3(0$# 5 4$%-0+ 2'0-3&' 2'$   31 2- 2'$   0-"$11-0(1:
.* 7 !- 0# '(1 ' ..$,1 %2$0 5 4$%-0+ "/3(1(2(-, (1 "-+.*$2$ (% 2'$
#(&(2 * 1(&, * .0-"$11-0 (, 2'$ .0-"$11-0 1712$+ 0$/3$121 2'$ 5 4$%-0+
Processor System;'$ .0-"$11-0 1712$+ "-,2 (,1  +("0-.0-:
"$11-0 2' 2 "-,20-*1 2'$ $,2(0$ (,1203+$,2 2 (,"*3#$1 2'$ %(0+5 0$ 2 *1-
(,"*3#$1  (,2$0% "$ -3 " , 0$.0-&0 + 2'$ %(0+5 0$ %0-+ 0$+-2$
"-,20-**$0 31(,& 2'$  ,# , $62$0, * 1-%25 0$ . ") &$
'$ .0-"$11-0 *1- (,"*3#$1 #(&(2 * 1(&, * .0-"$11-0 '(1 1(&, * .0-"$11-0
.0-"$11$1 $ "' 5 4$%-0+ 1 #(0$"2$# !7 2'$ 1712$+ .0-"$11-0  4$%-0+1
,# ,7 2$62 2- !$ #(1.* 7$# 0$ . 11$# -, 2- 2'$ #(1.* 7 1712$+ '$ 
 0-"$11-0(1.* 7 !- 0# "-,2 (,1 !-2' 2'$ .0-"$11-0 ,# #(1.* 7
1712$+1
Display System;$62 ,# 5 4$%-0+1 0$ .0-"$11$# !7 #(%%$0$,2 . 021 -%
2'$ #(1.* 7 "(0"3(207 '$ #(1.* 7 1712$+ 1$,#1 2'$ 2$62 ,# 5 4$%-0+ (,%-0:
+ 2(-, 2- 2'$ 23!$ 11$+!*7 1 4(#$- 1(&, * '$ #(1.* 7 1712$+ *1-
&$,$0 2$1 ,# 1$,#1 4$02(" *  ,# '-0(8-,2 *  17," 1(&, *1
2- 2'$ 23!$ 11$+!*7  :"-+. 2(!*$ 4(#$- -32.32 (1 2 2'$ 0$ 0 -% 2'$
(&(2(8(,& 1"(**-1"-.$
Voltage Controlled Oscillator (VCO)
 12$0 "*-")1 %-0 2'$ "/3(1(2(-, 1712$+ 0$ &$,$0 2$# !7 4-*2 &$ "-,:
20-**$# -1"(** 2-0 -, 2'$   - 0# ,# "(0"3(207 -, 2'$  "/3(1(2(-,
!- 0# '$ "(0"3(207 + )$1 3. .' 1$# *-")$# *--. '$ + 12$0 "*-") (1
#(4(#$# #-5, !7 2'$  "/3(1(2(-, "(0"3(207 3,#$0 "-,20-* -% 2'$ .0-"$11-0
1712$+