The Active-Filter Tuned Oscillator

** Circuit Description **

* op-amp subcircuit

.subckt uA741         1 2 3 4 5
* connections:        | | | | |
*                     | | | | |
*   non-inverting input | | | |
*         inverting input | | |
*     positive power supply | |
*       negative power supply |
*                        output
*
*
  c1   11 12 8.661E-12
  c2    6  7 30.00E-12
  dc    5 53 dx
  de   54  5 dx
  dlp  90 91 dx
  dln  92 90 dx
  dp    4  3 dx
  egnd 99  0 poly(2) (3,0) (4,0) 0 .5 .5
  fb    7 99 poly(5) vb vc ve vlp vln 0 10.61E6 -10E6 10E6 10E6 -10E6
  ga    6  0 11 12 188.5E-6
  gcm   0  6 10 99 5.961E-9
  iee  10  4 dc 15.16E-6
  hlim 90  0 vlim 1K
  q1   11  2 13 qx
  q2   12  1 14 qx
  r2    6  9 100.0E3
  rc1   3 11 5.305E3
  rc2   3 12 5.305E3
  re1  13 10 1.836E3
  re2  14 10 1.836E3
  ree  10 99 13.19E6
  ro1   8  5 50
  ro2   7 99 100
  rp    3  4 18.16E3
  vb    9  0 dc 0
  vc    3 53 dc 1
  ve   54  4 dc 1
  vlim  7  8 dc 0
  vlp  91  0 dc 40
  vln   0 92 dc 40
.model dx D(Is=800.0E-18 Rs=1)
.model qx NPN(Is=800.0E-18 Bf=93.75)
.ends uA741

** Main Circuit **
* power supplies
Vcc 8 0 DC +15V
Vee 9 0 DC -15V
* high-Q filter circuit
Xopamp1 3 5 8 9 1 uA741
Xopamp2 7 5 8 9 4 uA741
R1 2 3 50k
C1 3 0 16nF IC=0V
R2 3 4 10k
C2 4 5 16nF IC=0V
R3 5 1 10k
R4 1 7 10k
R5 7 0 10k
* diode limiter circuit 
D1 0 2 D1N4148
D2 2 0 D1N4148
R6 1 2 10k
* model statement
.model D1N4148 D (Is=0.1p Rs=16 CJO=2p Tt=12n Bv=100 Ibv=0.1p)
** Analysis Requests **
.OPTIONS itl5=0
.TRAN 20us 50ms 45ms 20us UIC
.FOUR 1kHz V(1)
** Output Requests **
.PLOT TRAN V(1) V(2)
.probe V(1) V(2)
.end