EFJohnson 7780 Two-Way Radio User Manual


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4-1
November 1999
Part No. 001-7780-500
CIRCUIT DESCRIPTION
SECTION 4 CIRCUIT DESCRIPTION
127($EORFNGLDJUDPRIWKH5)DQGORJLFXQLWVLV
ORFDWHGRQSDJH
4.1 POWER SWITCHING AND REGULATION
4.1.1 POWER SWITCHING
8QVZLWFKHGEDWWHU\ YROWDJHLVDSSOLHGWRWKH
SRZHUDPSOLILHUP RGXOH DQGSRZHUFRQWUROFLUFXLWLQ
WKH5)XQLW2WKHUZLVHDOOSRZHU LVVZLWFKHGE\
3FKDQQHO026)(7V 4DQG4LQWKHOR JLF 
XQLW7KH/9&&VXSSO\LVSURGXFHGE\4DQGWKH
9&&VXSSO\LVSURGXFHGE\ 4:KHQWKHRQRII
VZLWFKLVWXUQHGRQWKHRXWSXWRI VZLWFKLQJWUDQVL VWRU
4JRHVORZZKLFKWXUQV4DQG4RQ7KLV
DSSOLHVVZLWFKHGYROWV WR Y ROWUHJXODWRU V,&
DQG,&WKHDXGLRDP SOLILHUVWDJHVDQGRW KHUSDU WV 
RIWKHWUDQVFHLYHU
:KHQWKHSRZHUVZLWFKLV WXUQHGRIIWKHEDV H RI
4LVSXOOHGORZE\5ZKLFKWXUQV4RIIDQG
WKHFROOHF WRUJRHVKLJK+RZHYHUEHFDXVHRIGLRGH
'4DQG4GRQRWWXUQRIIXQWLO&
FKDUJHVWKURXJK57KLVSUR YLGHVDVOLJKWW XUQ RII
GHOD\ WRJLYHWKHPLFURSURFHVVRUWLPHWRWDNHRYHU
SRZHURIIFRQWURO7KHPLFURSURFHVVRULPPHGLDWHO\
GHWHFWVSRZHUWXUQRII E\PRQLWR ULQJW KH2))5(4, 
VLJQDORQSLQ,W WKHQFKDQJHVWKH 2))5(4RXWSXW
RQSLQWRDKLJKOHYHOZKLFKWXUQV4DJ DLQRQ
XQWLOFXUUHQWVHWWLQJVKDYH EHHQVDYHGWRPHPRU\DQG
RWKHUUHTXLUH GSRZHUGRZQIXQFWLR QVKD YHEHHQ
SHUIRUPHG
4.1.2 5-VOLT REGULATORS (IC401, IC402)
5HJXODWRU,&LQWKHORJL FXQLWSUR YLGHVWKH
/9ORJLFVXSSO\DQGUHJ XODWRU,&SUR YLGHV
WKH9VXSSO\7KH9VXSSO\LVLQWXUQVZLWFKHG
E\44WR SURYLGHWKH5979DQG6
VXSSOLHV7KHVHWUDQVLVWRU VDUHFRQWUROO HGE\VLJQDOV 
IURPWKHPLFURSURFHVVRU
7KHORZEDWWHU\GH WHFWVLJQDOLVSU RYLGH GE\D
YROWDJHGLYLGHUIR UPHGE\5D QG57KHVH
UHVLVWRUVGLYLGHGRZ QWKH99FFV XSSO\WRSURGXFH
WKH%$7,1VLJQDOWKDWLV DSSOLHGWRSLQRIWKH
PLFURSURFHVVRU
4.2 SYNTHESIZER DESCRIPTION
4.2.1 INTRODUCTION
7KHV\QWKH VL]HUR XWSXWVLJQD OLVSURGXFHGE\D 
9&29ROWDJH&R QWUROOHG2VFLOOD WRULQWKH5)XQLW
7KH9&2IUHTXHQF\LVFR QWUROO HGE\D'&YROWDJH 
SURGXFHGE\WKHSKDVHGHWHF WRU LQV\QWKHVL] HUFKLS
,&7KHSKDVHGHWH FWRUVHQV HVWKH SKDVHDQG
IUHTXHQF\RIWKHWZ RLQSXWVLJQDOV2QHVL JQDOLVWKH
UHIHUHQFHIUHTXHQF\IURP7&;2;DQGWKHRWKHULV
IURPWKH9 &2,IWKHVHVLJQD OVDUHQRWWKHVDP H
IUHTXHQF\WKHSKDVHGHWHFWRUFKDQJHVW KH9&2
FRQWUROYROWDJHZKLFKF KDQJHVWKH9&2IUHTXHQF\
XQWLOERWKVLJQDOVDUHV\QFKURQL]HG7KH9&2LVWKHQ
³ORFNHG´RQI UHTXHQF\
&KDQQHOVDUHVHOHFWHGE\SURJUDPPLQJWKH
FRXQWHUVLQ,&WRGLYLGHE\GLIIHUHQWQXPEHUV7KLV
SURJUDPPLQJGDWDFRPHVIURPWKHPLFURSURFHVVRURQ
WKHORJLF ERDUG7KHIUHTXHQF\ VWDELOLW\RIW KHV\QWKH
VL]HULQERW KWKHUHFHLYHDQGWUD QVPLWPRGHVL VGHWHU
PLQHGE\WKHVWDELOL W\RI7&;2;7KHVWD ELOLW\RI
WKLVGHYLFH LV330IURP± WR)± WR
&7KH9&2RXWSXWVLJQDOLVEXIIHUHGD QGWKHQ
IHGWRWKHUH FHLYHUDVWKHILUVW LQMHFWLR QVLJQD ODQGWR
WKHWUDQVPLWWHUDVW KHWUDQV PLWVLJQDO
4.2.2 VCO (IC3), BUFFERS (Q10-Q12)
6XSSO\YROWDJHWR9&2, &LVIURP&39UH JX
ODWRU,&DQGDF WLYHILOWH U4RQWKH,)ERDUG4
IXQFWLRQVDVDF DSDFLWDQFHP XOWLSOLHUWRSURYLGH
ILOWHULQJRIWKHYROWVXSSO\WRWKH 9&25DQG]HQHU
GLRGH'SURYLGH ELDVDQG&SURYLGHVWKHFDSDFL
WDQFHWKDWLVPXOWLSOLHG,IDQRLVHSXOVHRURWKHU
YROWDJHFKDQJHDSSHDUV RQWKHFROOHF WRUWKHEDVH
YROWDJHGRHVQRWFKDQJHEHFDXVHRI&DQG'7KHUH
IRUHLWGRHVQRWDSSHDURQWKH  HPLWWHU
7KH9&2FRQWURO YROWDJHLVDSSOLHGWRSLQRI
,&DQGWKHWUDQVPLWDXGLRGDWDPRGXODWLRQVLJQDO LV
DSSOLHGWRSLQ7KHPRGXODWLRQVLJQDO LVDOVRDSSOLHG
WRWKH7&;2DVGHVFULEHGLQWKHQH[WVHF WLRQ7KH
RXWSXWVLJQDORI WKH9&2RQSLQLVDSSOLH GWRD
7VSOLWWHUIRU PHGE\557KLV QHWZRUNURXWHVWKH
9&2VLJQDOWRE XIIHUDPSOLILHUV44DQGDOVRWR
47KHVHVWDJHVSURYLGHDP SOLILFDWLRQD QG LVRODWH
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