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VCO buffer

Discussion in 'Electronic Design' started by Andrew Holme, Jan 18, 2009.

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  1. Andrew Holme

    Andrew Holme Guest

    I'm designing a 40-70 MHz synthesizer using the Mini-Circuits POS-75 VCO.
    The VCO output varies from 9 dBm at 40 MHz down to 7 dBm at 70 MHz. My
    circuit needs to provide isolation, tolerate open and short-circuit loads,
    and deliver 15 dBm into 50 ohms across the tuning range. What do folks
    think of the solution below? In particular, what about C2? This "hack"
    seems to compensate for the input level variation; but I don't know if it
    will work for real. This is for very low volume production and C2 could be
    set-on-test.


    Version 4
    SHEET 1 1308 680
    WIRE -304 48 -400 48
    WIRE -240 48 -304 48
    WIRE -112 48 -176 48
    WIRE 48 48 -32 48
    WIRE 160 48 48 48
    WIRE 272 48 160 48
    WIRE 480 48 368 48
    WIRE 624 48 480 48
    WIRE 976 48 864 48
    WIRE 1072 48 976 48
    WIRE -400 80 -400 48
    WIRE 480 80 480 48
    WIRE 624 80 624 48
    WIRE 864 80 864 48
    WIRE 48 144 48 48
    WIRE 160 144 160 48
    WIRE 1072 160 1072 48
    WIRE 480 192 480 160
    WIRE 624 192 624 160
    WIRE 624 192 480 192
    WIRE -400 224 -400 160
    WIRE 320 224 320 112
    WIRE 624 224 624 192
    WIRE -400 352 -400 304
    WIRE 48 352 48 208
    WIRE 160 352 160 224
    WIRE 320 352 320 304
    WIRE 624 352 624 304
    WIRE 864 352 864 160
    WIRE 1072 352 1072 240
    FLAG 320 352 0
    FLAG -400 352 0
    FLAG 624 352 0
    FLAG 160 352 0
    FLAG 1072 352 0
    FLAG -304 48 IN
    FLAG 976 48 OUT
    FLAG 864 352 0
    FLAG 48 352 0
    SYMBOL voltage 624 208 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V2
    SYMATTR Value 12
    SYMBOL voltage 320 208 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V3
    SYMATTR Value 3.3
    SYMBOL res 144 128 R0
    SYMATTR InstName R3
    SYMATTR Value 100
    SYMBOL cap -176 32 R90
    WINDOW 0 0 32 VBottom 0
    WINDOW 3 32 32 VTop 0
    SYMATTR InstName C1
    SYMATTR Value 1n
    SYMBOL res -16 32 R90
    WINDOW 0 0 56 VBottom 0
    WINDOW 3 32 56 VTop 0
    SYMATTR InstName R4
    SYMATTR Value 50
    SYMBOL res 1056 144 R0
    SYMATTR InstName R5
    SYMATTR Value 50
    SYMBOL res -384 176 R180
    WINDOW 0 36 76 Left 0
    WINDOW 3 36 40 Left 0
    SYMATTR InstName R7
    SYMATTR Value 50
    SYMBOL ind2 608 64 R0
    SYMATTR InstName L1
    SYMATTR Value 16µ
    SYMATTR Type ind
    SYMBOL ind2 848 64 R0
    SYMATTR InstName L2
    SYMATTR Value 1µ
    SYMATTR Type ind
    SYMBOL npn 368 112 M270
    SYMATTR InstName Q1
    SYMATTR Value 2N3904
    SYMBOL res 464 64 R0
    SYMATTR InstName R1
    SYMATTR Value 800
    SYMBOL cap 32 144 R0
    SYMATTR InstName C2
    SYMATTR Value 150p
    SYMBOL voltage -400 208 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V1
    SYMATTR Value SINE(0 1.4 70e6)
    TEXT -248 192 Left 0 !.tran 0 150n 50n
    TEXT 696 48 Left 0 !K L1 L2 1
    TEXT 648 8 Left 0 ;Mini-Circuits T16-1
    TEXT -344 344 Left 0 ;or SINE(0 1.8 40e6)
     
  2. Andrew Holme

    Andrew Holme Guest

    Done.
     
  3. Guest

    All that for a clock for an FPGA? Which FPGA has a sine wave clock
    input rated in dBm???
     
  4. Andrew Holme

    Andrew Holme Guest

    No and none.

    I'm using an LVDS-output comparator for that.

    The sine wave output goes elsewhere.
     
  5. JosephKK

    JosephKK Guest

    A LOT of people have lost the a.b.* tree due to a few over aggressive
    state AGs and wimp ISPs. Damn, have you no memory?
     
  6. Nobody

    Nobody Guest

    More like AGs giving ISPs an excuse to stop providing a service which has
    significant overhead[1] yet which most of their customers never use.

    [1] 4.6TB/day, which equates to roughly 500Mbit/sec continuous bandwidth
    usage, plus all of the servers and RAID arrays needed to process and store
    all that data.
     
  7. Their excuse was to get rid of the alleged "kiddie porn". This is
    ludicrous - everybody knows that the best "kiddie porn" is on IRC. >:->

    Cheers!
    Rich
     
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