synrad-rf-driver.sch 6.89 KB
v 20130925 2
C 40000 40000 0 0 0 title-A3.sym
C 43800 48000 1 0 0 resistor-2.sym
{
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device=RESISTOR
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refdes=R2
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value=309
}
C 46300 48000 1 0 0 resistor-2.sym
{
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device=RESISTOR
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refdes=R4
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value=9.1
}
C 45100 47600 1 270 0 resistor-2.sym
{
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device=RESISTOR
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refdes=R3
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value=500
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comment=0-1000 Ohm
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documentation=Bias
}
C 42100 48000 1 0 0 resistor-2.sym
{
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device=RESISTOR
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refdes=R1
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value=1K
}
C 49100 47200 1 0 0 inductor-1.sym
{
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device=INDUCTOR
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refdes=L2
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symversion=0.1
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value=50nH
}
C 48700 50400 1 270 0 inductor-1.sym
{
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device=INDUCTOR
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refdes=L1
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symversion=0.1
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value=90nH
}
C 48300 49500 1 90 0 capacitor-1.sym
{
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device=CAPACITOR
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refdes=C2
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symversion=0.1
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value=1500pF
}
C 52000 46300 1 90 0 capacitor-1.sym
{
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device=CAPACITOR
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refdes=C6
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symversion=0.1
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value=150pF
}
C 52000 47600 1 90 0 capacitor-1.sym
{
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device=CAPACITOR
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refdes=C4
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symversion=0.1
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value=3pF
}
C 46200 46700 1 90 0 capacitor-1.sym
{
T 45500 46900 5 10 0 0 90 0 1
device=CAPACITOR
T 46400 47500 5 10 1 1 180 0 1
refdes=C1
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symversion=0.1
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value=1uF
}
C 50800 46300 1 90 0 capacitor-1.sym
{
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device=CAPACITOR
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refdes=C5
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symversion=0.1
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value=80pF
T 50200 45600 5 10 1 1 0 0 1
comment=15-150pF
T 50300 45900 5 10 1 1 0 0 1
documentation=Tuning
}
C 52000 48700 1 0 0 capacitor-1.sym
{
T 52200 49400 5 10 0 0 0 0 1
device=CAPACITOR
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refdes=C3
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symversion=0.1
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value=1000pF
}
C 48300 47900 1 0 0 nmos-3.sym
{
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device=SUB_CIRCUIT
T 48900 48300 5 10 1 1 0 0 1
refdes=XQ1
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value=ARF446
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comment=MRF150
}
C 43600 46700 1 90 0 zener-1.sym
{
T 43000 47100 5 10 0 0 90 0 1
device=ZENER_DIODE
T 42900 47500 5 10 1 1 180 0 1
refdes=D1
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value=1N751
T 42600 47000 5 10 1 1 0 0 1
comment=5.1V
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description=1N751A
}
C 41200 46400 1 0 0 vdc-1.sym
{
T 40700 46850 5 10 1 1 0 0 1
refdes=Vsw
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device=VOLTAGE_SOURCE
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footprint=none
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value=DC 30V
}
C 41200 49000 1 0 0 vdc-1.sym
{
T 40600 49450 5 10 1 1 0 0 1
refdes=Vosc
T 41900 49850 5 10 0 0 0 0 1
device=VOLTAGE_SOURCE
T 41900 50050 5 10 0 0 0 0 1
footprint=none
T 40500 49150 5 10 1 1 0 0 1
value=DC 30V
}
C 50100 48800 1 0 0 txline4-1.sym
{
T 50200 48700 5 10 0 1 0 0 1
device=TLIN
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refdes=TL1
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documentation=1/4 wave transformer
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comment=Zo = 26.7
T 50100 48800 5 10 0 0 0 0 1
value=Z0=26.7 F=50MEG NL=0.25
}
C 49900 48500 1 0 0 gnd-1.sym
C 50900 48500 1 0 0 gnd-1.sym
C 48000 45700 1 0 0 gnd-1.sym
C 48000 49200 1 0 0 gnd-1.sym
C 48700 47600 1 0 0 gnd-1.sym
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C 41400 48700 1 0 0 gnd-1.sym
C 41400 46100 1 0 0 gnd-1.sym
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Ferrit
Bead
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C 53700 48400 1 270 0 resistor-2.sym
{
T 54050 48000 5 10 0 0 270 0 1
device=RESISTOR
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refdes=Rload
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value=50
}
C 53700 47200 1 0 0 gnd-1.sym
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T 50800 40900 9 18 1 0 0 0 1
Synrad CO2 Laser - RF Driver IV
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1
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1
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synrad-rf-driver.sch
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2015 - 02 - 08
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M.S.Waters
C 43000 49200 1 0 0 spice-model-1.sym
{
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device=model
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refdes=A1
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model-name=1N751A
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file=../../lib/diode/1n751.mod
}
C 53100 45900 1 0 0 spice-model-1.sym
{
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device=model
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refdes=A2
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model-name=MRF150
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file=../../lib/mosfet/arf446.mod
}
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It seems that there are no good SPICE models for an RF power MOSFET
such as the MRF150. So I've had to analyse this circuit by disecting it
eg. isolating and analysing the feedback path. And by using MOSFET
models that can be modeled ie. for the DC operating point.
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The feedback path incorporates a
first order bandpass notch filter. The
center frequency, Fo is set using C5.
At the center frequency the pole/zero
pair cancel and so the phase change
is zero. The table to the right contains
simulation results where C5 has been
varied and the notch filter center
frequency (Fo) has been determined.
The relationship between C5 and Fo
is approximately linear.
T 44400 40600 9 10 1 0 0 0 10
C5 (pF)
----------
    10
    20
    40
    60
    80
  100
  120
  150
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Fo (MHz)
------------
  56.45
  54.19
  51.68
  48.63
  46.81
  44.86
  43.17
  40.91

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Synrad calls TL1 a 1/4
wave transformer. I
think this means it's a
90 deg. phase shifter.
Positive feedback is
required to generate
the oscillator action.
(TL1 would need to be
1.5m long at 50MHz.)

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